Carbon supported Pt-Ru catalysts were prepared by potentiostatic deposition at -0.5 V from H2PtCl6 + RuCl3 in H2SO4 solution in the presence of ethylene glycol (EG), ethanol (EtOH) and formic acid (HCOOH) as stabilizing agents. The active surface area of the Pt-Ru catalyst was determined by Cu-UPD. The highest value was obtained with HCOOH added, followed by EtOH, and EG. SEM and AFM images showed that the mean particle size of the Pt-Ru nanoparticles was three or four times smaller in the presence of a stabilizer. Electrocatalytic activity measurements indicated that the most active electrode for methanol electrooxidation was obtained with EtOH as additive, followed by EG. The electrode prepared with HCOOH additive gave lower catalytic activity than that without stabilizing agent.