diff --git a/moto/dynamodb2/responses.py b/moto/dynamodb2/responses.py
index 493e17833..e2f1ef1cc 100644
--- a/moto/dynamodb2/responses.py
+++ b/moto/dynamodb2/responses.py
@@ -204,9 +204,9 @@ class DynamoHandler(BaseResponse):
                 if cond_items:
                     expected = {}
                     overwrite = False
-                    exists_re = re.compile('^attribute_exists\((.*)\)$')
+                    exists_re = re.compile('^attribute_exists\s*\((.*)\)$')
                     not_exists_re = re.compile(
-                        '^attribute_not_exists\((.*)\)$')
+                        '^attribute_not_exists\s*\((.*)\)$')
 
                 for cond in cond_items:
                     exists_m = exists_re.match(cond)
@@ -556,9 +556,9 @@ class DynamoHandler(BaseResponse):
 
                 if cond_items:
                     expected = {}
-                    exists_re = re.compile('^attribute_exists\((.*)\)$')
+                    exists_re = re.compile('^attribute_exists\s*\((.*)\)$')
                     not_exists_re = re.compile(
-                        '^attribute_not_exists\((.*)\)$')
+                        '^attribute_not_exists\s*\((.*)\)$')
 
                 for cond in cond_items:
                     exists_m = exists_re.match(cond)
diff --git a/tests/test_dynamodb2/test_dynamodb.py b/tests/test_dynamodb2/test_dynamodb.py
index 70feaf7f6..afc919dd7 100644
--- a/tests/test_dynamodb2/test_dynamodb.py
+++ b/tests/test_dynamodb2/test_dynamodb.py
@@ -700,8 +700,8 @@ def test_filter_expression():
     filter_expr = moto.dynamodb2.comparisons.get_filter_expression('Id IN :v0', {}, {':v0': {'NS': [7, 8, 9]}})
     filter_expr.expr(row1).should.be(True)
 
-    # attribute function tests
-    filter_expr = moto.dynamodb2.comparisons.get_filter_expression('attribute_exists(Id) AND attribute_not_exists(User)', {}, {})
+    # attribute function tests (with extra spaces)
+    filter_expr = moto.dynamodb2.comparisons.get_filter_expression('attribute_exists(Id) AND attribute_not_exists (User)', {}, {})
     filter_expr.expr(row1).should.be(True)
 
     filter_expr = moto.dynamodb2.comparisons.get_filter_expression('attribute_type(Id, N)', {}, {})