Copper is known as a unique metal electrode which effectively reduces CO2 to CH4, C2H4 and alcohols in aqueous electrolytes with intermediate formation of adsorbed CO. Voltammetric measurements revealed that CO is adsorbed on Cu electrodes below -0.7 V vs. nhe accompanied with quasi-reversible electron transfer. CO is not adsorbed above -0.7 V on Cu electrode. Proton is involved with the adsorption process. Other metal electrodes (Au, Ag, Ni, Zn, Cd, Sn and Pb) did not show such activity for CO adsorption accompanied with electron transfer. In situ FTIR spectroscopic measurements indicated that adsorbed CO is present with C-O stretching adsorption band at 2087 cm-1 on Cu electrode below -0.7 V. Analysis of experimental results suggest that CO is likely to be adsorbed in a hydridocarbonyl complex on Cu electrode without net electron transfer to CO molecule. The surface complex formation may be a preceding step to electrochemical reduction of CO to hydrocarbons and alcohols.