The role of alkali cations (Li+, Na+ K+ Cs+, and Be2+) on the blank voltammetric response and the oxidative stripping of carbon monoxide from stepped Pt single-crystal electrodes in alkaline media has been investigated by cyclic voltammetry. A strong influence of the nature of the cation on both the blank voltammetric profile and the CO oxidation is observed and related to the influence of the cation on the specific adsorption of OH on the platinum surface. Especially Li+ and Be2+ cations markedly affect the adsorption of OH and thereby have a significant promoting effect on COads oxidation. The voltammetric experiments suggest that, on Pt(111), the influence of Li+ (and Be2+) is primarily through a weakening of the repulsive interactions between the OH in the OH adlayer, whereas in the presence of steps also, the onset of OH adsorption is at a lower potential, both on steps and on terraces.