diff --git a/README.md b/README.md
index 88fd1ff..10da1e0 100644
--- a/README.md
+++ b/README.md
@@ -162,6 +162,15 @@ if err := cl.Connect(); err != nil {
 }
 ```
 
+### Custom logger
+
+You can specifiy custom logger for client. Logger must implement `Logger` interface. Provide logger during client init:
+
+```go
+cl := New(cfg, adc.WithLogger(myCustomLogger))
+```
+
+
 ## Contributing
 
 1. Create new PR from `main` branch
diff --git a/adc.go b/adc.go
index 914e643..de4a422 100644
--- a/adc.go
+++ b/adc.go
@@ -4,7 +4,6 @@ package adc
 import (
 	"crypto/tls"
 	"errors"
-	"fmt"
 	"strings"
 	"time"
 
@@ -19,6 +18,7 @@ const (
 type Client struct {
 	cfg    *Config
 	ldapCl ldap.Client
+	logger Logger
 }
 
 // Creates new client and populate provided config and options.
@@ -29,6 +29,7 @@ func New(cfg *Config, opts ...Option) *Client {
 			Users:   DefaultUsersConfigs(),
 			Groups:  DefaultGroupsConfigs(),
 		},
+		logger: &nopLogger{},
 	}
 
 	// Apply options
@@ -42,6 +43,12 @@ func New(cfg *Config, opts ...Option) *Client {
 	return cl
 }
 
+// Client logger interface.
+type Logger interface {
+	Debug(args ...interface{})
+	Debugf(template string, args ...interface{})
+}
+
 type Option func(*Client)
 
 // Specifies ldap client for AD client.
@@ -49,6 +56,11 @@ func WithLdapClient(l ldap.Client) Option {
 	return func(cl *Client) { cl.ldapCl = l }
 }
 
+// Specifies custom logger for client.
+func WithLogger(l Logger) Option {
+	return func(cl *Client) { cl.logger = l }
+}
+
 func (cl *Client) Config() *Config {
 	return cl.cfg
 }
@@ -57,7 +69,7 @@ func (cl *Client) Config() *Config {
 func (cl *Client) Connect() error {
 	conn, err := cl.connect(cl.cfg.Bind)
 	if err != nil {
-		return fmt.Errorf("can't connect: %s", err.Error())
+		return err
 	}
 	cl.ldapCl = conn
 	return nil
diff --git a/group.go b/group.go
index 77e21d1..c00a0ef 100644
--- a/group.go
+++ b/group.go
@@ -148,6 +148,7 @@ func (g *Group) MembersId() []string {
 	return result
 }
 
+// Adds provided accounts IDs to provided group members. Returns number of addedd accounts.
 func (cl *Client) AddGroupMembers(groupId string, membersIds ...string) (int, error) {
 	group, err := cl.GetGroup(&GetGroupequest{Id: groupId})
 	if err != nil {
@@ -158,27 +159,41 @@ func (cl *Client) AddGroupMembers(groupId string, membersIds ...string) (int, er
 	}
 
 	ch := make(chan string, len(membersIds))
+	errCh := make(chan error, len(membersIds))
 	wg := &sync.WaitGroup{}
+
 	for _, id := range membersIds {
 		wg.Add(1)
-		go func(userId string, ch chan<- string, wg *sync.WaitGroup) {
+		go func(userId string, ch chan<- string, errCh chan<- error, wg *sync.WaitGroup) {
 			defer wg.Done()
 			user, err := cl.GetUser(&GetUserRequest{Id: userId})
 			if err != nil {
+				errCh <- fmt.Errorf("can't get account '%s': %s", userId, err.Error())
 				return
 			}
 			if user == nil {
+				cl.logger.Debugf("Account '%s' being added to '%s' wasn't found",
+					userId, groupId)
 				return
 			}
 			if user.IsGroupMember(groupId) {
+				cl.logger.Debugf("The adding account '%s' is already a member of the group '%s'",
+					userId, groupId)
 				return
 			}
 			ch <- user.DN
-		}(id, ch, wg)
+		}(id, ch, errCh, wg)
 	}
 	wg.Wait()
+	close(errCh)
 	close(ch)
 
+	for err := range errCh {
+		if err != nil {
+			return 0, err
+		}
+	}
+
 	var toAdd []string
 	for dn := range ch {
 		toAdd = append(toAdd, dn)
@@ -188,6 +203,10 @@ func (cl *Client) AddGroupMembers(groupId string, membersIds ...string) (int, er
 	}
 
 	newMembers := popAddGroupMembers(group, toAdd)
+
+	cl.logger.Debugf("Adding new group members to '%s'; Old count: %d; New count: %d",
+		groupId, len(group.MembersId()), len(newMembers))
+
 	if err := cl.updateAttribute(group.DN, "member", newMembers); err != nil {
 		return 0, err
 	}
@@ -205,6 +224,7 @@ func popAddGroupMembers(g *Group, toAdd []string) []string {
 	return result
 }
 
+// Deletes provided accounts IDs from provided group members. Returns number of deleted from group members.
 func (cl *Client) DeleteGroupMembers(groupId string, membersIds ...string) (int, error) {
 	group, err := cl.GetGroup(&GetGroupequest{Id: groupId})
 	if err != nil {
@@ -215,27 +235,41 @@ func (cl *Client) DeleteGroupMembers(groupId string, membersIds ...string) (int,
 	}
 
 	ch := make(chan string, len(membersIds))
+	errCh := make(chan error, len(membersIds))
 	wg := &sync.WaitGroup{}
+
 	for _, id := range membersIds {
 		wg.Add(1)
-		go func(userId string, ch chan<- string, wg *sync.WaitGroup) {
+		go func(userId string, ch chan<- string, errCh chan<- error, wg *sync.WaitGroup) {
 			defer wg.Done()
 			user, err := cl.GetUser(&GetUserRequest{Id: userId})
 			if err != nil {
+				errCh <- fmt.Errorf("can't get account '%s': %s", userId, err.Error())
 				return
 			}
 			if user == nil {
+				cl.logger.Debugf("Account '%s' being deleted from '%s' wasn't found",
+					userId, groupId)
 				return
 			}
 			if !user.IsGroupMember(groupId) {
+				cl.logger.Debugf("The deleting account '%s' already isn't a member of the group '%s'",
+					userId, groupId)
 				return
 			}
 			ch <- user.DN
-		}(id, ch, wg)
+		}(id, ch, errCh, wg)
 	}
 	wg.Wait()
+	close(errCh)
 	close(ch)
 
+	for err := range errCh {
+		if err != nil {
+			return 0, err
+		}
+	}
+
 	var toDel []string
 	for dn := range ch {
 		toDel = append(toDel, dn)
@@ -245,6 +279,10 @@ func (cl *Client) DeleteGroupMembers(groupId string, membersIds ...string) (int,
 	}
 
 	newMembers := popDelGroupMembers(group, toDel)
+
+	cl.logger.Debugf("Deleting members from group '%s'; Old count: %d; New count: %d",
+		groupId, len(group.MembersId()), len(newMembers))
+
 	if err := cl.updateAttribute(group.DN, "member", newMembers); err != nil {
 		return 0, err
 	}
diff --git a/group_test.go b/group_test.go
index 7c30588..fd486d1 100644
--- a/group_test.go
+++ b/group_test.go
@@ -108,14 +108,16 @@ func Test_AddGroupMembers(t *testing.T) {
 	added, err := cl.AddGroupMembers("group1", "userFake")
 	require.NoError(t, err)
 	require.Equal(t, 0, added)
+
 	// Error user
-	added, err = cl.AddGroupMembers("group1", "user2")
-	require.NoError(t, err)
-	require.Equal(t, 0, added)
+	_, err = cl.AddGroupMembers("group1", "user2")
+	require.Error(t, err)
+
 	// Already member user
 	added, err = cl.AddGroupMembers("group1", "user1")
 	require.NoError(t, err)
 	require.Equal(t, 0, added)
+
 	// Ok user
 	added, err = cl.AddGroupMembers("group1", "user3")
 	require.NoError(t, err)
@@ -152,14 +154,16 @@ func Test_DeleteGroupMembers(t *testing.T) {
 	deleted, err := cl.DeleteGroupMembers("group1", "userFake")
 	require.NoError(t, err)
 	require.Equal(t, 0, deleted)
+
 	// Error user
-	deleted, err = cl.DeleteGroupMembers("group1", "user2")
-	require.NoError(t, err)
-	require.Equal(t, 0, deleted)
+	_, err = cl.DeleteGroupMembers("group1", "user2")
+	require.Error(t, err)
+
 	// Already not member user
 	deleted, err = cl.DeleteGroupMembers("group1", "user3")
 	require.NoError(t, err)
 	require.Equal(t, 0, deleted)
+
 	// Ok user
 	deleted, err = cl.DeleteGroupMembers("group1", "user1")
 	require.NoError(t, err)
diff --git a/mock.go b/mock.go
index 6cf2204..5206747 100644
--- a/mock.go
+++ b/mock.go
@@ -9,6 +9,12 @@ import (
 	"github.com/go-ldap/ldap/v3"
 )
 
+// Dummy not operational logger.
+type nopLogger struct{}
+
+func (l *nopLogger) Debug(args ...interface{})                   {}
+func (l *nopLogger) Debugf(template string, args ...interface{}) {}
+
 // Mock client. Implements ldap client interface.
 type mockClient struct {
 }