diff --git a/boards/forms.py b/boards/forms.py
--- a/boards/forms.py
+++ b/boards/forms.py
@@ -22,8 +22,6 @@ LAST_LOGIN_TIME = 'last_login_time'
 TEXT_PLACEHOLDER = _('Type message here. Use formatting panel for more advanced usage.')
 TAGS_PLACEHOLDER = _('tag1 several_words_tag')
 
-ERROR_IMAGE_DUPLICATE = _('Such image was already posted')
-
 LABEL_TITLE = _('Title')
 LABEL_TEXT = _('Text')
 LABEL_TAG = _('Tag')
@@ -149,10 +147,6 @@ class PostForm(NeboardForm):
                     _('Image must be less than %s bytes')
                     % str(board_settings.MAX_IMAGE_SIZE))
 
-            image_hash = PostImage.get_hash(image)
-            if PostImage.objects.filter(hash=image_hash).exists():
-                raise forms.ValidationError(ERROR_IMAGE_DUPLICATE)
-
         return image
 
     def clean(self):
diff --git a/boards/models/post.py b/boards/models/post.py
--- a/boards/models/post.py
+++ b/boards/models/post.py
@@ -103,10 +103,17 @@ class PostManager(models.Manager):
             post, post.poster_ip))
 
         if image:
-            post_image = PostImage.objects.create(image=image)
+            # Try to find existing image. If it exists, assign it to the post
+            # instead of createing the new one
+            image_hash = PostImage.get_hash(image)
+            existing = PostImage.objects.filter(hash=image_hash)
+            if len(existing) > 0:
+                post_image = existing[0]
+            else:
+                post_image = PostImage.objects.create(image=image)
+                logger.info('Created new image #{} for post #{}'.format(
+                            post_image.id, post.id))
             post.images.add(post_image)
-            logger.info('Created image #{} for post #{}'.format(
-                post_image.id, post.id))
 
         thread.replies.add(post)
         list(map(thread.add_tag, tags))
@@ -352,7 +359,10 @@ class Post(models.Model, Viewable):
         thread with all posts is deleted.
         """
 
-        self.images.all().delete()
+        for image in self.images.all():
+            image_refs_count = Post.objects.filter(images__in=[image]).count()
+            if image_refs_count == 1:
+                image.delete()
 
         if self.is_opening():
             self.get_thread().delete()