A model for impedance of the PEM fuel cell cathode including the effects of oxygen transport in the cathode catalyst layer, gas-diffusion layer and in the air channel is developed. The model confirms recent experimental result (I. Schneider et al., J. Electrochem. Soc., 154, B383 (2007)), showing that oxygen transport in the channel manifests itself as a low-frequency arc in the impedance spectrum. Furthermore, the model spectrum exhibits a sequence of closed loops due to the interference of the local and transported with the flow oxygen concentration disturbances. The mechanism of this effect is discussed. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.066207jes] All rights reserved.