The dependence of the electrocatalytic properties of Pt-Ru alloy nanoparticles supported on boron-doped diamond electrodes, on the electrodeposition conditions used to prepare them with respect to the oxidation of methanol was studied. Routes involving sequential and simultaneous deposition of the two elements were studied, and the effect of deposition potential was also examined. The morphology of the electrodeposits was characterized by scanning electron microscopy, and shows spherical Pt-Ru nanoparticles for simultaneous deposition and a dendritic structure for sequential deposition. The Pt-Ru binary catalysts from both deposition methods exhibit higher electrocatalytic activity than Pt alone. However, deposits from simultaneous deposition show higher chemical stability and catalytic activity for methanol oxidation than those prepared using sequential deposition, for which significant electrodissolution of Ru is a problem. The optimal Pt:Ru ratio in simultaneous deposition is seen for intermediate deposition potentials. The different morphologies and microstructures for the two deposition methods are also reflected in differing rate-determining steps for methanol oxidization as judged from Tafel analysis. Overall, a sensitive dependence of catalytic properties on electrodeposition parameters is indicated. (C) 2011 Elsevier B.V. All rights reserved.