2-Benzylindenes are hydrogenated to 2-benzylindanes using tris-(triphenylphosphine)-rhodium(I)-chloride in benzene by a strict cis-1,2 addition of hydrogen to the double bond. Thus, stereo- and region-specific deuterium labelling at the five-membered ring of various 2-benzylindanes has been carried out. The high selectivity of deuterium incorporation is shown independently by 1H NMR and mass (MIKE) spectrometry of selected 2-benzylindanes.