The distribution of H-2, CO, CH4 and C2H4 produced by electrochemical reduction of CO2 in aqueous KHCO3 solution at Cu electrodes has been studied in combination with the electrode surface analysis by X-ray photoelectron spectroscopy. Electrolyses were performed mainly at 1.9 V vs. SCE with Cu electrodes pretreated in various ways : ultrasonically cleaned, air-oxidized and electrolytically cleaned. The product distribution depended drastically on the pretreatment method and the electrolysis time. The heavily oxidized electrode surface produced H, predominantly, while the surface with a relatively large amount of metallic Cu gave preferential CO production. The surface with metallic Cu, Cu oxide and much adsorbed oxygen had an enhanced activity for hydrocarbon production. The oxide film at the surface was gradually reduced to bare Cu metal with increasing electrolysis time, resulting in a variation of the product distribution.