diff --git a/scrapy/contrib/pipeline/files.py b/scrapy/contrib/pipeline/files.py
index 8c43982a1fa..db8cf8b76dc 100644
--- a/scrapy/contrib/pipeline/files.py
+++ b/scrapy/contrib/pipeline/files.py
@@ -9,9 +9,13 @@
 import time
 from six.moves.urllib.parse import urlparse
 from collections import defaultdict
-from cStringIO import StringIO
 import six
 
+try:
+    from cStringIO import StringIO as BytesIO
+except ImportError:
+    from io import BytesIO
+
 from twisted.internet import defer, threads
 
 from scrapy import log
@@ -257,7 +261,7 @@ def get_media_requests(self, item, info):
 
     def file_downloaded(self, response, request, info):
         path = self.file_path(request, response=response, info=info)
-        buf = StringIO(response.body)
+        buf = BytesIO(response.body)
         self.store.persist_file(path, buf, info)
         checksum = md5sum(buf)
         return checksum
diff --git a/scrapy/contrib/pipeline/images.py b/scrapy/contrib/pipeline/images.py
index e955e72bf75..9c1a5445500 100644
--- a/scrapy/contrib/pipeline/images.py
+++ b/scrapy/contrib/pipeline/images.py
@@ -5,9 +5,13 @@
 """
 
 import hashlib
-from cStringIO import StringIO
 import six
 
+try:
+    from cStringIO import StringIO as BytesIO
+except ImportError:
+    from io import BytesIO
+
 from PIL import Image
 
 from scrapy.utils.misc import md5sum
@@ -70,7 +74,7 @@ def image_downloaded(self, response, request, info):
 
     def get_images(self, response, request, info):
         path = self.file_path(request, response=response, info=info)
-        orig_image = Image.open(StringIO(response.body))
+        orig_image = Image.open(BytesIO(response.body))
 
         width, height = orig_image.size
         if width < self.MIN_WIDTH or height < self.MIN_HEIGHT:
@@ -97,7 +101,7 @@ def convert_image(self, image, size=None):
             image = image.copy()
             image.thumbnail(size, Image.ANTIALIAS)
 
-        buf = StringIO()
+        buf = BytesIO()
         image.save(buf, 'JPEG')
         return image, buf
 
diff --git a/scrapy/contrib_exp/downloadermiddleware/decompression.py b/scrapy/contrib_exp/downloadermiddleware/decompression.py
index 6fad5b9b14a..c08f50b5ff3 100644
--- a/scrapy/contrib_exp/downloadermiddleware/decompression.py
+++ b/scrapy/contrib_exp/downloadermiddleware/decompression.py
@@ -6,10 +6,15 @@
 import gzip
 import zipfile
 import tarfile
-from cStringIO import StringIO
 from tempfile import mktemp
+
 import six
 
+try:
+    from cStringIO import StringIO as BytesIO
+except ImportError:
+    from io import BytesIO
+
 from scrapy import log
 from scrapy.responsetypes import responsetypes
 
@@ -27,7 +32,7 @@ def __init__(self):
         }
 
     def _is_tar(self, response):
-        archive = StringIO(response.body)
+        archive = BytesIO(response.body)
         try:
             tar_file = tarfile.open(name=mktemp(), fileobj=archive)
         except tarfile.ReadError:
@@ -38,7 +43,7 @@ def _is_tar(self, response):
         return response.replace(body=body, cls=respcls)
 
     def _is_zip(self, response):
-        archive = StringIO(response.body)
+        archive = BytesIO(response.body)
         try:
             zip_file = zipfile.ZipFile(archive)
         except zipfile.BadZipfile:
@@ -50,7 +55,7 @@ def _is_zip(self, response):
         return response.replace(body=body, cls=respcls)
 
     def _is_gzip(self, response):
-        archive = StringIO(response.body)
+        archive = BytesIO(response.body)
         try:
             body = gzip.GzipFile(fileobj=archive).read()
         except IOError:
diff --git a/scrapy/core/downloader/handlers/ftp.py b/scrapy/core/downloader/handlers/ftp.py
index 6b5f03bda70..6ac02cc2b3b 100644
--- a/scrapy/core/downloader/handlers/ftp.py
+++ b/scrapy/core/downloader/handlers/ftp.py
@@ -29,8 +29,8 @@
 """
 
 import re
+from io import BytesIO
 from six.moves.urllib.parse import urlparse
-from cStringIO import StringIO
 
 from twisted.internet import reactor
 from twisted.protocols.ftp import FTPClient, CommandFailed
@@ -42,7 +42,7 @@
 class ReceivedDataProtocol(Protocol):
     def __init__(self, filename=None):
         self.__filename = filename
-        self.body = open(filename, "w") if filename else StringIO()
+        self.body = open(filename, "w") if filename else BytesIO()
         self.size = 0
 
     def dataReceived(self, data):
@@ -54,7 +54,7 @@ def filename(self):
         return self.__filename
 
     def close(self):
-        self.body.close() if self.filename else self.body.reset()
+        self.body.close() if self.filename else self.body.seek(0)
 
 _CODE_RE = re.compile("\d+")
 class FTPDownloadHandler(object):
diff --git a/scrapy/core/downloader/handlers/http11.py b/scrapy/core/downloader/handlers/http11.py
index 455794b14b6..b803af1dce0 100644
--- a/scrapy/core/downloader/handlers/http11.py
+++ b/scrapy/core/downloader/handlers/http11.py
@@ -2,8 +2,8 @@
 
 import re
 
+from io import BytesIO
 from time import time
-from cStringIO import StringIO
 from six.moves.urllib.parse import urldefrag
 
 from zope.interface import implements
@@ -234,7 +234,7 @@ def __init__(self, finished, txresponse, request):
         self._finished = finished
         self._txresponse = txresponse
         self._request = request
-        self._bodybuf = StringIO()
+        self._bodybuf = BytesIO()
 
     def dataReceived(self, bodyBytes):
         self._bodybuf.write(bodyBytes)
diff --git a/scrapy/mail.py b/scrapy/mail.py
index a5d936ab31c..e1d7c44f672 100644
--- a/scrapy/mail.py
+++ b/scrapy/mail.py
@@ -3,7 +3,7 @@
 
 See documentation in docs/topics/email.rst
 """
-from cStringIO import StringIO
+from six.moves import cStringIO as StringIO
 import six
 
 from email.utils import COMMASPACE, formatdate
diff --git a/scrapy/responsetypes.py b/scrapy/responsetypes.py
index ac0559a5034..16479896fcb 100644
--- a/scrapy/responsetypes.py
+++ b/scrapy/responsetypes.py
@@ -6,7 +6,7 @@
 
 from mimetypes import MimeTypes
 from pkgutil import get_data
-from cStringIO import StringIO
+from io import BytesIO
 import six
 
 from scrapy.http import Response
@@ -34,7 +34,7 @@ def __init__(self):
         self.classes = {}
         self.mimetypes = MimeTypes()
         mimedata = get_data('scrapy', 'mime.types')
-        self.mimetypes.readfp(StringIO(mimedata))
+        self.mimetypes.readfp(BytesIO(mimedata))
         for mimetype, cls in six.iteritems(self.CLASSES):
             self.classes[mimetype] = load_object(cls)
 
diff --git a/scrapy/tests/test_contrib_exporter.py b/scrapy/tests/test_contrib_exporter.py
index d50544c51b8..9092007e50e 100644
--- a/scrapy/tests/test_contrib_exporter.py
+++ b/scrapy/tests/test_contrib_exporter.py
@@ -1,6 +1,6 @@
 import unittest, json
+from io import BytesIO
 from six.moves import cPickle as pickle
-from cStringIO import StringIO
 import lxml.etree
 import re
 
@@ -19,7 +19,7 @@ class BaseItemExporterTest(unittest.TestCase):
 
     def setUp(self):
         self.i = TestItem(name=u'John\xa3', age='22')
-        self.output = StringIO()
+        self.output = BytesIO()
         self.ie = self._get_exporter()
 
     def _get_exporter(self, **kwargs):
@@ -126,13 +126,13 @@ def _check_output(self):
     def test_export_multiple_items(self):
         i1 = TestItem(name='hello', age='world')
         i2 = TestItem(name='bye', age='world')
-        f = StringIO()
+        f = BytesIO()
         ie = PickleItemExporter(f)
         ie.start_exporting()
         ie.export_item(i1)
         ie.export_item(i2)
         ie.finish_exporting()
-        f.reset()
+        f.seek(0)
         self.assertEqual(pickle.load(f), i1)
         self.assertEqual(pickle.load(f), i2)
 
@@ -151,21 +151,21 @@ def _check_output(self):
         self.assertCsvEqual(self.output.getvalue(), 'age,name\r\n22,John\xc2\xa3\r\n')
 
     def test_header(self):
-        output = StringIO()
+        output = BytesIO()
         ie = CsvItemExporter(output, fields_to_export=self.i.fields.keys())
         ie.start_exporting()
         ie.export_item(self.i)
         ie.finish_exporting()
         self.assertCsvEqual(output.getvalue(), 'age,name\r\n22,John\xc2\xa3\r\n')
 
-        output = StringIO()
+        output = BytesIO()
         ie = CsvItemExporter(output, fields_to_export=['age'])
         ie.start_exporting()
         ie.export_item(self.i)
         ie.finish_exporting()
         self.assertCsvEqual(output.getvalue(), 'age\r\n22\r\n')
 
-        output = StringIO()
+        output = BytesIO()
         ie = CsvItemExporter(output)
         ie.start_exporting()
         ie.export_item(self.i)
@@ -173,7 +173,7 @@ def test_header(self):
         ie.finish_exporting()
         self.assertCsvEqual(output.getvalue(), 'age,name\r\n22,John\xc2\xa3\r\n22,John\xc2\xa3\r\n')
 
-        output = StringIO()
+        output = BytesIO()
         ie = CsvItemExporter(output, include_headers_line=False)
         ie.start_exporting()
         ie.export_item(self.i)
@@ -186,7 +186,7 @@ class TestItem2(Item):
             friends = Field()
 
         i = TestItem2(name='John', friends=['Mary', 'Paul'])
-        output = StringIO()
+        output = BytesIO()
         ie = CsvItemExporter(output, include_headers_line=False)
         ie.start_exporting()
         ie.export_item(i)
@@ -216,7 +216,7 @@ def _check_output(self):
         self.assertXmlEquivalent(self.output.getvalue(), expected_value)
 
     def test_multivalued_fields(self):
-        output = StringIO()
+        output = BytesIO()
         item = TestItem(name=[u'John\xa3', u'Doe'])
         ie = XmlItemExporter(output)
         ie.start_exporting()
@@ -226,7 +226,7 @@ def test_multivalued_fields(self):
         self.assertXmlEquivalent(output.getvalue(), expected_value)
 
     def test_nested_item(self):
-        output = StringIO()
+        output = BytesIO()
         i1 = TestItem(name=u'foo\xa3hoo', age='22')
         i2 = TestItem(name=u'bar', age=i1)
         i3 = TestItem(name=u'buz', age=i2)
@@ -248,7 +248,7 @@ def test_nested_item(self):
         self.assertXmlEquivalent(output.getvalue(), expected_value)
 
     def test_nested_list_item(self):
-        output = StringIO()
+        output = BytesIO()
         i1 = TestItem(name=u'foo')
         i2 = TestItem(name=u'bar')
         i3 = TestItem(name=u'buz', age=[i1, i2])
diff --git a/scrapy/tests/test_contrib_feedexport.py b/scrapy/tests/test_contrib_feedexport.py
index 7a1b3dc8f0d..bf4943bfab3 100644
--- a/scrapy/tests/test_contrib_feedexport.py
+++ b/scrapy/tests/test_contrib_feedexport.py
@@ -1,6 +1,6 @@
 import os
+from io import BytesIO
 from six.moves.urllib.parse import urlparse
-from cStringIO import StringIO
 
 from zope.interface.verify import verifyObject
 from twisted.trial import unittest
@@ -62,13 +62,13 @@ def test_store(self):
     def _assert_stores(self, storage, path):
         spider = Spider("default")
         file = storage.open(spider)
-        file.write("content")
+        file.write(b"content")
         yield storage.store(file)
         self.failUnless(os.path.exists(path))
-        self.failUnlessEqual(open(path).read(), "content")
+        self.failUnlessEqual(open(path).read(), b"content")
         # again, to check s3 objects are overwritten
-        yield storage.store(StringIO("new content"))
-        self.failUnlessEqual(open(path).read(), "new content")
+        yield storage.store(BytesIO(b"new content"))
+        self.failUnlessEqual(open(path).read(), b"new content")
 
 
 class S3FeedStorageTest(unittest.TestCase):
@@ -93,9 +93,9 @@ class StdoutFeedStorageTest(unittest.TestCase):
 
     @defer.inlineCallbacks
     def test_store(self):
-        out = StringIO()
+        out = BytesIO()
         storage = StdoutFeedStorage('stdout:', _stdout=out)
         file = storage.open(Spider("default"))
-        file.write("content")
+        file.write(b"content")
         yield storage.store(file)
-        self.assertEqual(out.getvalue(), "content")
+        self.assertEqual(out.getvalue(), b"content")
diff --git a/scrapy/tests/test_downloadermiddleware_httpcompression.py b/scrapy/tests/test_downloadermiddleware_httpcompression.py
index 5fbc2c6194e..8a0e75d9032 100644
--- a/scrapy/tests/test_downloadermiddleware_httpcompression.py
+++ b/scrapy/tests/test_downloadermiddleware_httpcompression.py
@@ -1,6 +1,6 @@
+from io import BytesIO
 from unittest import TestCase
 from os.path import join, abspath, dirname
-from cStringIO import StringIO
 from gzip import GzipFile
 
 from scrapy.spider import Spider
@@ -104,8 +104,8 @@ def test_process_response_encoding_inside_body(self):
             'Content-Type': 'text/html',
             'Content-Encoding': 'gzip',
         }
-        f = StringIO()
-        plainbody = """<html><head><title>Some page</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312">"""
+        f = BytesIO()
+        plainbody = b"""<html><head><title>Some page</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312">"""
         zf = GzipFile(fileobj=f, mode='wb')
         zf.write(plainbody)
         zf.close()
@@ -122,8 +122,8 @@ def test_process_response_force_recalculate_encoding(self):
             'Content-Type': 'text/html',
             'Content-Encoding': 'gzip',
         }
-        f = StringIO()
-        plainbody = """<html><head><title>Some page</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312">"""
+        f = BytesIO()
+        plainbody = b"""<html><head><title>Some page</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312">"""
         zf = GzipFile(fileobj=f, mode='wb')
         zf.write(plainbody)
         zf.close()
diff --git a/scrapy/tests/test_log.py b/scrapy/tests/test_log.py
index 9367fb953ff..f0b57b806a9 100644
--- a/scrapy/tests/test_log.py
+++ b/scrapy/tests/test_log.py
@@ -1,4 +1,4 @@
-from cStringIO import StringIO
+from io import BytesIO
 
 from twisted.python import log as txlog, failure
 from twisted.trial import unittest
@@ -21,7 +21,7 @@ class ScrapyFileLogObserverTest(unittest.TestCase):
     encoding = 'utf-8'
 
     def setUp(self):
-        self.f = StringIO()
+        self.f = BytesIO()
         self.log_observer = log.ScrapyFileLogObserver(self.f, self.level, self.encoding)
         self.log_observer.start()
 
diff --git a/scrapy/tests/test_mail.py b/scrapy/tests/test_mail.py
index 250ae04aee4..58d44bdb35e 100644
--- a/scrapy/tests/test_mail.py
+++ b/scrapy/tests/test_mail.py
@@ -1,6 +1,6 @@
 import unittest
+from io import BytesIO
 
-from cStringIO import StringIO
 from scrapy.mail import MailSender
 
 class MailSenderTest(unittest.TestCase):
@@ -30,8 +30,8 @@ def test_send_html(self):
         self.assertEqual(msg.get('Content-Type'), 'text/html')
 
     def test_send_attach(self):
-        attach = StringIO()
-        attach.write('content')
+        attach = BytesIO()
+        attach.write(b'content')
         attach.seek(0)
         attachs = [('attachment', 'text/plain', attach)]
 
diff --git a/scrapy/tests/test_pipeline_images.py b/scrapy/tests/test_pipeline_images.py
index 511d0f50e4c..a3b1059ef34 100644
--- a/scrapy/tests/test_pipeline_images.py
+++ b/scrapy/tests/test_pipeline_images.py
@@ -1,8 +1,7 @@
 import os
 import hashlib
 import warnings
-from cStringIO import StringIO
-from tempfile import mkdtemp
+from tempfile import mkdtemp, TemporaryFile
 from shutil import rmtree
 
 from twisted.trial import unittest
@@ -201,7 +200,7 @@ class TestItem(Item):
 
 
 def _create_image(format, *a, **kw):
-    buf = StringIO()
+    buf = TemporaryFile()
     Image.new(*a, **kw).save(buf, format)
     buf.seek(0)
     return Image.open(buf)
diff --git a/scrapy/tests/test_spider.py b/scrapy/tests/test_spider.py
index 8abc3962843..903eff7b19f 100644
--- a/scrapy/tests/test_spider.py
+++ b/scrapy/tests/test_spider.py
@@ -1,8 +1,8 @@
 import gzip
 import inspect
 import warnings
-from cStringIO import StringIO
 from scrapy.utils.trackref import object_ref
+from io import BytesIO
 
 from twisted.trial import unittest
 
@@ -57,7 +57,7 @@ class XMLFeedSpiderTest(SpiderTest):
     spider_class = XMLFeedSpider
 
     def test_register_namespace(self):
-        body = """<?xml version="1.0" encoding="UTF-8"?>
+        body = b"""<?xml version="1.0" encoding="UTF-8"?>
         <urlset xmlns:x="http://www.google.com/schemas/sitemap/0.84"
                 xmlns:y="http://www.example.com/schemas/extras/1.0">
         <url><x:loc>http://www.example.com/Special-Offers.html</loc><y:updated>2009-08-16</updated><other value="bar" y:custom="fuu"/></url>
@@ -103,7 +103,7 @@ class CSVFeedSpiderTest(SpiderTest):
 
 class CrawlSpiderTest(SpiderTest):
 
-    test_body = """<html><head><title>Page title<title>
+    test_body = b"""<html><head><title>Page title<title>
     <body>
     <p><a href="item/12.html">Item 12</a></p>
     <div class='links'>
@@ -195,8 +195,8 @@ class SitemapSpiderTest(SpiderTest):
 
     spider_class = SitemapSpider
 
-    BODY = "SITEMAP"
-    f = StringIO()
+    BODY = b"SITEMAP"
+    f = BytesIO()
     g = gzip.GzipFile(fileobj=f, mode='w+b')
     g.write(BODY)
     g.close()
diff --git a/scrapy/tests/test_utils_jsonrpc.py b/scrapy/tests/test_utils_jsonrpc.py
index 6eb60d1f44c..8902e9efa38 100644
--- a/scrapy/tests/test_utils_jsonrpc.py
+++ b/scrapy/tests/test_utils_jsonrpc.py
@@ -1,5 +1,5 @@
 import unittest, json
-from cStringIO import StringIO
+from io import BytesIO
 
 from scrapy.utils.jsonrpc import jsonrpc_client_call, jsonrpc_server_call, \
     JsonRpcError, jsonrpc_errors
@@ -19,7 +19,7 @@ def __init__(self, result=None, error=None):
     def urlopen(self, url, request):
         self.url = url
         self.request = request
-        return StringIO(self.response)
+        return BytesIO(self.response)
 
 class TestTarget(object):
 
diff --git a/scrapy/tests/test_utils_misc/__init__.py b/scrapy/tests/test_utils_misc/__init__.py
index 143c9b6445b..18fc6d5329e 100644
--- a/scrapy/tests/test_utils_misc/__init__.py
+++ b/scrapy/tests/test_utils_misc/__init__.py
@@ -1,7 +1,6 @@
 import sys
 import os
 import unittest
-from cStringIO import StringIO
 
 from scrapy.item import Item, Field
 from scrapy.utils.misc import load_object, arg_to_iter, walk_modules
diff --git a/scrapy/utils/gz.py b/scrapy/utils/gz.py
index aa8ffc6fca9..741948359c5 100644
--- a/scrapy/utils/gz.py
+++ b/scrapy/utils/gz.py
@@ -1,5 +1,10 @@
 import struct
-from cStringIO import StringIO
+
+try:
+    from cStringIO import StringIO as BytesIO
+except ImportError:
+    from io import BytesIO
+
 from gzip import GzipFile
 
 def gunzip(data):
@@ -7,9 +12,9 @@ def gunzip(data):
 
     This is resilient to CRC checksum errors.
     """
-    f = GzipFile(fileobj=StringIO(data))
-    output = ''
-    chunk = '.'
+    f = GzipFile(fileobj=BytesIO(data))
+    output = b''
+    chunk = b'.'
     while chunk:
         try:
             chunk = f.read(8196)
diff --git a/scrapy/utils/iterators.py b/scrapy/utils/iterators.py
index 92717d9bcc7..150b077aef3 100644
--- a/scrapy/utils/iterators.py
+++ b/scrapy/utils/iterators.py
@@ -1,5 +1,9 @@
-import re, csv
-from cStringIO import StringIO
+import re, csv, six
+
+try:
+    from cStringIO import StringIO as BytesIO
+except ImportError:
+    from io import BytesIO
 
 from scrapy.http import TextResponse, Response
 from scrapy.selector import Selector
@@ -48,7 +52,7 @@ def csviter(obj, delimiter=None, headers=None, encoding=None):
     def _getrow(csv_r):
         return [str_to_unicode(field, encoding) for field in next(csv_r)]
 
-    lines = StringIO(_body_or_str(obj, unicode=False))
+    lines = BytesIO(_body_or_str(obj, unicode=False))
     if delimiter:
         csv_r = csv.reader(lines, delimiter=delimiter)
     else:
@@ -68,7 +72,7 @@ def _getrow(csv_r):
 
 
 def _body_or_str(obj, unicode=True):
-    assert isinstance(obj, (Response, basestring)), \
+    assert isinstance(obj, (Response, six.string_types)), \
         "obj must be Response or basestring, not %s" % type(obj).__name__
     if isinstance(obj, Response):
         if not unicode:
@@ -77,7 +81,7 @@ def _body_or_str(obj, unicode=True):
             return obj.body_as_unicode()
         else:
             return obj.body.decode('utf-8')
-    elif type(obj) is type(u''):
+    elif isinstance(obj, six.text_type):
         return obj if unicode else obj.encode('utf-8')
     else:
         return obj.decode('utf-8') if unicode else obj