diff --git a/livesync/indico_livesync/initial.py b/livesync/indico_livesync/initial.py
index 536d236..594bb88 100644
--- a/livesync/indico_livesync/initial.py
+++ b/livesync/indico_livesync/initial.py
@@ -41,7 +41,7 @@ def apply_acl_entry_strategy(rel, principal):
 
 
 def _get_excluded_category_filter(event_model=Event):
-    if excluded_category_ids := get_excluded_categories():
+    if excluded_category_ids := get_excluded_categories(deep=True):
         return event_model.category_id.notin_(excluded_category_ids)
     return True
 
diff --git a/livesync/indico_livesync/simplify.py b/livesync/indico_livesync/simplify.py
index 48de859..30af2d5 100644
--- a/livesync/indico_livesync/simplify.py
+++ b/livesync/indico_livesync/simplify.py
@@ -135,7 +135,7 @@ def _process_cascaded_category_contents(records):
 
     :param records: queue records to process
     """
-    excluded_categories = get_excluded_categories()
+    excluded_categories = get_excluded_categories(deep=True)
     excluded_categories_filter = Event.category_id.notin_(excluded_categories) if excluded_categories else True
 
     category_prot_records = {rec.category_id for rec in records if rec.type == EntryType.category
diff --git a/livesync/indico_livesync/util.py b/livesync/indico_livesync/util.py
index 8571a11..8555a61 100644
--- a/livesync/indico_livesync/util.py
+++ b/livesync/indico_livesync/util.py
@@ -9,8 +9,9 @@ from datetime import timedelta
 
 from werkzeug.datastructures import ImmutableDict
 
+from indico.core.db import db
 from indico.modules.attachments.models.attachments import Attachment
-from indico.modules.categories.models.categories import Category
+from indico.modules.categories import Category
 from indico.modules.events import Event
 from indico.modules.events.contributions.models.contributions import Contribution
 from indico.modules.events.contributions.models.subcontributions import SubContribution
@@ -78,7 +79,17 @@ def clean_old_entries():
 
 
 @memoize_request
-def get_excluded_categories():
-    """Get excluded category IDs."""
+def get_excluded_categories(*, deep=False):
+    """Get excluded category IDs.
+
+    :param deep: Whether to get all subcategory ids as well
+    """
     from indico_livesync.plugin import LiveSyncPlugin
-    return {int(x['id']) for x in LiveSyncPlugin.settings.get('excluded_categories')}
+    ids = {int(x['id']) for x in LiveSyncPlugin.settings.get('excluded_categories')}
+    if not deep or not ids:
+        return ids
+    cte = Category.get_tree_cte()
+    query = (db.session.query(Category.id)
+             .join(cte, Category.id == cte.c.id)
+             .filter(cte.c.path.overlap(ids), ~cte.c.is_deleted))
+    return {x.id for x in query}
diff --git a/livesync/tests/util_test.py b/livesync/tests/util_test.py
index 281ca0e..af80adc 100644
--- a/livesync/tests/util_test.py
+++ b/livesync/tests/util_test.py
@@ -11,7 +11,7 @@ from indico.util.date_time import now_utc
 
 from indico_livesync.models.queue import ChangeType, EntryType, LiveSyncQueueEntry
 from indico_livesync.plugin import LiveSyncPlugin
-from indico_livesync.util import clean_old_entries
+from indico_livesync.util import clean_old_entries, get_excluded_categories
 
 
 def test_clean_old_entries(dummy_event, db, dummy_agent):
@@ -34,3 +34,17 @@ def test_clean_old_entries(dummy_event, db, dummy_agent):
     clean_old_entries()
     assert LiveSyncQueueEntry.query.filter_by(processed=False).count() == 10
     assert LiveSyncQueueEntry.query.filter_by(processed=True).count() == 3
+
+
+def test_get_excluded_categories(dummy_category, create_category):
+    cat1 = create_category()
+    cat1a = create_category(parent=cat1)
+    cat1aa = create_category(parent=cat1a)
+    cat1b = create_category(parent=cat1)
+    cat2 = create_category()
+    LiveSyncPlugin.settings.set('excluded_categories', [{'id': cat1.id}])
+    assert get_excluded_categories() == {cat1.id}
+    assert get_excluded_categories(deep=True) == {cat1.id, cat1a.id, cat1aa.id, cat1b.id}
+    LiveSyncPlugin.settings.set('excluded_categories', [{'id': 0}])
+    assert get_excluded_categories() == {0}
+    assert get_excluded_categories(deep=True) == {cat1.id, cat1a.id, cat1aa.id, cat1b.id, cat2.id, dummy_category.id, 0}