The electrochemical study of different supported and unsupported Pt-based catalysts used in polymer electrolyte fuel cells (PEMFCs) has been made by means of thin film rotating disk electrode (RDE) method. The comparison of electrochemical surface area (ESA) was made using cyclic voltammetry measurements in or at room temperature and scanning rates of 20 and . Oxygen reduction activity for aerogel-supported and carbon-supported Pt catalysts was evaluated at various rotation speeds in the range of and compared to the catalytic activity of unsupported Pt-black catalyst. The calculated values of Levich constant for the oxygen reduction reaction (ORR) indicate dependence on the applied voltage and either 4 or 2–4 electron transfer mechanism. The hydrogen peroxide by-product formation was determined with a rotating ring disk electrode (RRDE) and was observed to take place mostly at voltages below due to the limitations from mass transport effects. The results obtained at different Pt loadings in the range of Pt demonstrated that XC-72 and aerogel-based catalysts are foreseen to have higher ESA in comparison to other tested supported and unsupported commercially available catalysts.