Carbon-supported platinum catalysts (Pt/C) were prepared by treatment of PtO2/C under different conditions: (a) heating at 380 degrees C in air, argon and hydrogen; (b) electrochemical reduction in H2SO4; and (c) reduction with NaBH4. The effect of the preparation conditions on the structure and the catalytic activity of the catalysts for the electrooxidation of CH3OH in acid media was studied. The highest activity was achieved for the catalyst treated in air. The activity is determined by the crystal faces exposed at the particle surface as well as particle size and the partial oxidation of the carbon support.