Methanol oxidation in acid solution was studied at platinum single crystals, Pt(hkl), as the model catalyst, and at nanostructural platinum supported on high surface area carbon, Pt/C, as the real catalyst. The linear extrapolation method was used to determine the beginning of hydroxyl anion adsorption. Structural sensitivity of the adsorption was proved and a correlation with the onset of the methanol oxidation current was established at all catalysts. Bisulfate and chloride anions were found to decrease the methanol oxidation rate, but probably did not influence the reaction parth. The specific activity for the reaction increased in the sequence Pt(110) < Pt/C < Pt(111), suggesting that the activity of the supported Pt catalyst can be correlated with the activities of the dominating crystal planes on its surface.