Pt/carbon composite nanofibers were prepared by electrodepositing Pt nanoparticles onto electrospun carbon nanofibers and were used as catalysts towards the oxidation of methanol. The morphology and size of Pt nanoparticles were controlled by selectively adjusting the electrodeposition potential and time. SEM and TEM results show that the composite nanofibers were successfully obtained and Pt particle diameters were between 10 and 55 nm. The electrocatalytic activity of the composite nanofibers expressed by current density per Pt particle mass was found to depend on the particle size, showing an increasing activity when the catalyst diameter decreased. (C) 2009 Elsevier B.V. All rights reserved.