Ionic conductivity in the air cathode of a polymer electrolyte membrane (PEM) fuel cell changes with distance depending on the ionomer loading [J. Electrochem. Soc., 150, A1440 (2003)]. When the ionic conductivity changes with distance inside a porous electrode, existing models in the literature fail to capture the behavior of porous electrodes. In this paper, we show how existing models in the literature can be modified to take care of varying ionic conductivity. The modified model is shown to be efficient in handling mathematical singularity arising from the distribution of ionic conductivity inside a porous electrode. In addition, the model developed was used to optimize the functionality of ionic conductivity (ionomer loading) to minimize the ohmic drop across a porous electrode. It is shown that depending on the system parameters, there might be an optimum way to distribute the ionomer loading inside the PEM fuel cell cathode. (c) 2005 The Electrochemical Society.