A Pd electrode surface was modified with Cu and used for the electrochemical reduction of CO2 in aqueous KHCO3 solution. The effect of hydrogen absorption on the reaction has been clarified using the Cu-modified electrode. The current efficiencies for HCOOH, CH4 and CH3OH production were larger on hydrogenated Cu-modified Pd electrodes than on nonhydrogenated electrodes. However, the production of CO, C2H4 and C2H5OH was not enhanced by the absorption of hydrogen. The enhancement seemed to be caused not by the change in the surface morphology or the degree of oxidation of Cu but by the participation of absorbed hydrogen in the reduction of CO2.