The electrochemical oxidation of methanol has been investigated on underpotentially deposited-ruthenium-modified platinum electrode (upd-Ru/Pt) and on underpotentially deposited-tin-modified platinum electrode (upd-Sn/Pt). The submonolayers of upd-Ru and upd-Sn on a Pt electrode increased the rate of methanol electrooxidation several times as large as that on a pure Pt electrode. The best performance for methanol electrooxidation was obtained on a ternary platinum based catalyst modified by upd-Ru and upd-Sn simultaneously. The influence of the submonolayers of upd-Ru adatoms and upd-Sn adatoms on the oxidation of methanol in acid has been investigated. The effect of Ru on methanol electrooxidation lies on the distribution of Ru adatoms on a Pt surface. It has been shown that as long as the amount of upd-Ru deposits were controlled in a proper range, upd-Ru deposits would enhance the methanol oxidation obtained on a Pt electrode at whichever deposition potential the upd-Ru deposits were obtained. The effects of tin are sensible to the potential range. The enhancement effect of upd-Sn adatoms for the oxidation of methanol will disappear as the electrode potential is beyond a certain value. It is speculated that there exists a synergetic effect on the Pt electrode as adatoms Ru and Sn participate simultaneously in the methanol oxidation.