A model for the cathode catalyst layer (CCL) performance in a DMFC is developed. The electrochemical mechanism of methanol oxidation reaction (MOR) on the cathode side is assumed. Numerical solution shows that at small currents, MOR dominates in a narrow domain (virtual anode) close to the membrane, while the oxygen reduction runs mainly outside this domain. At small currents, the cathode represents a complete short-circuited fuel cell. At large currents, the electrode potential exhibits rapid linear decay with the current due to the dominating proton transport losses. A simple approximate equation for the CCL resistivity in this regime is obtained. Fitting this equation to the experimental polarization curves gives the CCL proton conductivity. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.033210jes] All rights reserved.