diff --git a/boards/models.py b/boards/models.py
--- a/boards/models.py
+++ b/boards/models.py
@@ -47,6 +47,8 @@ class PostManager(models.Manager):
 
         if tags:
             map(post.tags.add, tags)
+            for tag in tags:
+                tag.threads.add(post)
 
         if thread:
             thread.replies.add(post)