diff --git a/pylinac/picketfence.py b/pylinac/picketfence.py
index 60d3e049..690ce86d 100644
--- a/pylinac/picketfence.py
+++ b/pylinac/picketfence.py
@@ -171,7 +171,7 @@ class PFResult(ResultBase):
         title="Mean Picket Spacing (mm)",
     )
     offsets_from_cax_mm: list[float] = Field(
-        description="The offsets of each picket from the central axis in mm.",
+        description="The offsets of each picket from the central axis in mm. Positive is to the left.",
         title="Offsets from CAX (mm)",
     )
     passed: bool = Field(
@@ -189,7 +189,7 @@ class PFResult(ResultBase):
         description="The widths of the pickets in mm."
     )
     mlc_positions_by_leaf: dict[str, list[float]] = Field(
-        description="A dictionary where the key is the leaf number and the value is a list of positions in mm **from the CAX**. The distance is from the x-value (or y-value for left-right orientation) of the CAX. "
+        description="A dictionary where the key is the leaf number and the value is a list of positions in mm **from the CAX**. The distance is from the x-value (or y-value for left-right orientation) of the CAX. Positive is to the left."
         "Rotation of the MLCs would affect these distances."
     )
     mlc_errors_by_leaf: dict[str, list[float]] = Field(
@@ -1274,11 +1274,11 @@ def _generate_results_data(self) -> PFResult:
             leaf_items = list(group_iter)  # group_iter is a generator
             leaf_names = leaf_items[0].full_leaf_nums
             for idx, leaf_name in enumerate(leaf_names):
-                pos_vals = [
-                    m.position_mm[idx] - cax_physical_position for m in leaf_items
+                position_values = [
+                    cax_physical_position - m.position_mm[idx] for m in leaf_items
                 ]
                 error_vals = [m.error[idx] for m in leaf_items]
-                positions_by_leaf[str(leaf_name)] = pos_vals
+                positions_by_leaf[str(leaf_name)] = position_values
                 errors_by_leaf[str(leaf_name)] = error_vals
         errors_by_leaf = dict(
             sorted(errors_by_leaf.items())
diff --git a/tests_basic/test_picketfence.py b/tests_basic/test_picketfence.py
index a77574bf..e8f97207 100644
--- a/tests_basic/test_picketfence.py
+++ b/tests_basic/test_picketfence.py
@@ -157,7 +157,7 @@ def test_results_data(self):
         )  # 36 leaf pairs in the image
         # constancy check
         self.assertAlmostEqual(
-            statistics.mean(data.mlc_positions_by_leaf["17"]), 7.91, delta=0.1
+            statistics.mean(data.mlc_positions_by_leaf["17"]), -7.91, delta=0.1
         )
         # check max error matches a combination of the leaf values
         self.assertEqual(
@@ -175,6 +175,13 @@ def test_results_data(self):
         # shouldn't raise
         json.loads(data_str)
 
+        # check signs of leaf positions and picket positions from the CAX are the same.
+        self.assertAlmostEqual(
+            data_dict["mlc_positions_by_leaf"]["17"][0],
+            data_dict["offsets_from_cax_mm"][0],
+            delta=0.1,
+        )
+
     def test_no_measurements_suggests_inversion(self):
         file_loc = get_file_from_cloud_test_repo(
             [TEST_DIR, "noisy-FFF-wide-gap-pf.dcm"]
@@ -349,7 +356,7 @@ def test_bb_pf_combo(self):
         self.assertAlmostEqual(results.max_error_mm, 0.0, delta=0.005)
         self.assertAlmostEqual(results.cax.x, 636.5, delta=0.1)
         # bb is 2mm off in bb setup image above
-        self.assertAlmostEqual(results.mlc_positions_by_leaf["17"][0], -102, delta=0.1)
+        self.assertAlmostEqual(results.mlc_positions_by_leaf["17"][0], 102, delta=0.1)
 
 
 class LoadingFromMultiple(TestCase):