diff --git a/paratemp/coordinate_analysis.py b/paratemp/coordinate_analysis.py
index 5fcb954..6f361b3 100644
--- a/paratemp/coordinate_analysis.py
+++ b/paratemp/coordinate_analysis.py
@@ -207,6 +207,8 @@ def calculate_distances(self, *args, recalculate=False,
         first_group = self.select_atoms('protein and not protein')
         second_group = self.select_atoms('protein and not protein')
         column_names = []
+        groups_CoM = []
+        column_names_CoM = []
         if len(args) == 0 and len(kwargs) == 0:
             args = ['all']
         if len(args) != 0:
@@ -249,6 +251,14 @@ def calculate_distances(self, *args, recalculate=False,
                                               ' currently supported.\nAt your '
                                               'own risk you can try assigning '
                                               'to self._data[{}].'.format(key))
+                except TypeError:
+                    selections = []
+                    for g in atoms:
+                        sel_string = 'bynum ' + ' '.join([str(i) for i in g])
+                        selections.append(self.select_atoms(sel_string))
+                    groups_CoM.append(selections)
+                    column_names_CoM.append(key)
+                    continue
                 first_group += self.select_atoms('bynum '+str(atoms[0]))
                 second_group += self.select_atoms('bynum '+str(atoms[1]))
                 column_names += [key]
@@ -267,6 +277,14 @@ def calculate_distances(self, *args, recalculate=False,
                                                                        nc) +
                               '\nThis should not happen.\nPossibly invalid '
                               'atom selection.')
+        n_groups = len(groups_CoM)
+        n_group_names = len(column_names_CoM)
+        if not n_groups == n_group_names:
+            raise SyntaxError('Different numbers of atom groups or number'
+                              ' of column labels for CoM calculations'
+                              '({} and {}, respectively).\n'
+                              'This should not happen.'.format(n_groups,
+                                                               n_group_names))
         if self._num_frames != self.trajectory.n_frames:
             if self._verbosity:
                 print('Current trajectory has {} frames, '.format(
@@ -275,14 +293,21 @@ def calculate_distances(self, *args, recalculate=False,
                       '{} frames.'.format(self._num_frames))
             if not ignore_file_change:
                 raise FileChangedError()
-        dists = np.zeros((self._num_frames, n1))
+        dists = np.zeros((self._num_frames, n1 + n_groups))
+        positions_1 = np.zeros((n1+n_groups, 3), dtype=np.float32)
+        positions_2 = np.zeros((n1+n_groups, 3), dtype=np.float32)
         for i in range(self._num_frames):
             self.trajectory[i]
-            MDa.lib.distances.calc_bonds(first_group.positions,
-                                         second_group.positions,
+            positions_1[:n1] = first_group.positions
+            positions_2[:n1] = second_group.positions
+            for j, group in enumerate(groups_CoM):
+                positions_1[n1+j] = group[0].center_of_mass()
+                positions_2[n1+j] = group[1].center_of_mass()
+            MDa.lib.distances.calc_bonds(positions_1,
+                                         positions_2,
                                          box=self.dimensions,
                                          result=dists[i])
-        for i, column in enumerate(column_names):
+        for i, column in enumerate(column_names + column_names_CoM):
             self._data[column] = dists[:, i]
         if save_data:
             self.save_data()
diff --git a/tests/conftest.py b/tests/conftest.py
index 92d3d53..db29c4d 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -33,6 +33,12 @@ def ref_a_dists():
                            names=['a'], index_col=0)
 
 
+@pytest.fixture
+def ref_g_dists():
+    import numpy
+    return numpy.load('tests/ref-data/spc2-g-dists.npy')
+
+
 @pytest.fixture
 def ref_delta_g():
     return np.load('tests/ref-data/spc2-fes1d-delta-gs.npy')
diff --git a/tests/ref-data/spc2-g-dists.npy b/tests/ref-data/spc2-g-dists.npy
new file mode 100644
index 0000000..5306311
Binary files /dev/null and b/tests/ref-data/spc2-g-dists.npy differ
diff --git a/tests/test_coordinate_analysis.py b/tests/test_coordinate_analysis.py
index cd1faeb..21390e2 100644
--- a/tests/test_coordinate_analysis.py
+++ b/tests/test_coordinate_analysis.py
@@ -114,6 +114,12 @@ def test_distance_pbc(self, univ_pbc, ref_a_pbc_dists):
                                      read_data=False, save_data=False)
         assert np.isclose(ref_a_pbc_dists['a'], univ_pbc.data['a']).all()
 
+    def test_distances_com(self, univ, ref_g_dists):
+        univ.calculate_distances(
+            read_data=False, save_data=False,
+            g=((1, 2), (3, 4)))
+        assert np.isclose(ref_g_dists, univ.data).all()
+
     def test_calculate_distance_raises(self, univ):
         with pytest.raises(SyntaxError):
             univ.calculate_distances(1, read_data=False, save_data=False)
@@ -132,7 +138,6 @@ def test_calculate_distance_warns(self, univ):
                           match='following positional arguments were given'):
             univ.calculate_distances('fail', read_data=False, save_data=False)
 
-
     def test_fes_1d_data_str(self, univ_w_a, ref_delta_g, ref_bins):
         """
         :type univ_w_a: paratemp.coordinate_analysis.Universe