diff --git a/apps/course/migrations/0020_auto_20180202_1716.py b/apps/course/migrations/0020_auto_20180202_1716.py
new file mode 100644
index 00000000..1b7f63d8
--- /dev/null
+++ b/apps/course/migrations/0020_auto_20180202_1716.py
@@ -0,0 +1,48 @@
+# Generated by Django 2.0.2 on 2018-02-02 17:16
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+import polymorphic_tree.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('contenttypes', '0002_remove_content_type_name'),
+        ('course', '0019_auto_20180130_1630'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='coursecomment',
+            options={'base_manager_name': 'objects', 'ordering': ('tree_id', 'lft'), 'verbose_name': 'Комментарий курса', 'verbose_name_plural': 'Комментарии курсов'},
+        ),
+        migrations.AlterModelOptions(
+            name='lessoncomment',
+            options={'base_manager_name': 'objects', 'ordering': ('tree_id', 'lft'), 'verbose_name': 'Комментарий урока', 'verbose_name_plural': 'Комментарии уроков'},
+        ),
+        migrations.RemoveField(
+            model_name='coursecomment',
+            name='parent',
+        ),
+        migrations.RemoveField(
+            model_name='lessoncomment',
+            name='parent',
+        ),
+        migrations.AddField(
+            model_name='comment',
+            name='parent',
+            field=polymorphic_tree.models.PolymorphicTreeForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='children', to='course.Comment'),
+        ),
+        migrations.AddField(
+            model_name='comment',
+            name='polymorphic_ctype',
+            field=models.ForeignKey(editable=False, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='polymorphic_course.comment_set+', to='contenttypes.ContentType'),
+        ),
+        migrations.AlterField(
+            model_name='comment',
+            name='author',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL),
+        ),
+    ]
diff --git a/apps/course/models.py b/apps/course/models.py
index 2cbc6d27..954a8160 100644
--- a/apps/course/models.py
+++ b/apps/course/models.py
@@ -3,7 +3,7 @@ from django.db import models
 from django.utils import timezone
 from django.contrib.auth import get_user_model
 
-from mptt.models import MPTTModel, TreeForeignKey
+from polymorphic_tree.models import PolymorphicMPTTModel, PolymorphicTreeForeignKey
 
 from .manager import CategoryQuerySet
 
@@ -123,9 +123,10 @@ class Material(models.Model):
         ordering = ('title',)
 
 
-class Comment(MPTTModel):
-    author = models.ForeignKey(User, on_delete=models.PROTECT)
+class Comment(PolymorphicMPTTModel):
     content = models.TextField('Текст комментария', default='')
+    author = models.ForeignKey(User, on_delete=models.CASCADE)
+    parent = PolymorphicTreeForeignKey('self', null=True, blank=True, related_name='children', db_index=True, on_delete=models.PROTECT)
 
     created_at = models.DateTimeField(auto_now_add=True)
     update_at = models.DateTimeField(auto_now=True)
@@ -142,11 +143,9 @@ class Comment(MPTTModel):
 
     class MPTTMeta:
         order_insertion_by = ['-created_at']
-        abstract = True
 
 
 class CourseComment(Comment):
-    parent = TreeForeignKey('self', null=True, blank=True, related_name='children', db_index=True, on_delete=models.PROTECT)
     course = models.ForeignKey(Course, on_delete=models.CASCADE, related_name='comments')
 
     class Meta(Comment.Meta):
@@ -155,7 +154,6 @@ class CourseComment(Comment):
 
 
 class LessonComment(Comment):
-    parent = TreeForeignKey('self', null=True, blank=True, related_name='children', db_index=True, on_delete=models.PROTECT)
     lesson = models.ForeignKey(Lesson, on_delete=models.CASCADE, related_name='comments')
 
     class Meta(Comment.Meta):