The performance of cinchonidine (CD) and cinchonine (CN) as chiral modifiers in enantioselective hydrogenation over Pd/C were compared in different concentrations. The catalytic hydrogenation with CD always occurred in better cc and at faster rate than that with CN. The difference is not attributable to the adsorption properties of the modifiers, but to the intrinsic enantio differentiation that accompanies the reaction acceleration.