Platinum nanoparticles supported on multi-walled carbon nanotubes (PtNP/MWCNT) were prepared using the magnetron sputtering technique and used as electrocatalysts for oxygen reduction reaction (ORR). Cyclic voltammetry and the rotating disk electrode experiments were performed in 0.5 M H2SO4 and 0.1 M KOH solutions in order to investigate the electrochemical properties of the prepared catalysts. The composite catalyst samples were characterised by scanning electron microscopy (SEM) and X-ray diffraction. The SEM images showed a uniform distribution of Pt nanolayers on the surface of MWCNTs. Specific and mass activities of O-2 reduction were determined for PtNP/MWCNT composites and a comparison with commercial Pt/C catalyst and bulk Pt was made. The PtNP/MWCNT catalysts exhibited a high electrocatalytic activity for the four-electron reduction of oxygen to water. (C) 2013 Elsevier B.V. All rights reserved.