Water transport through the gas diffusion media of a proton exchange membrane fuel cell (PEMFC) was investigated with a focus on the role of the microporous layer (MPL) coated on the cathode gas diffusion layer (GDL) The capillary pressure of the MPL and GDL which plays a significant role in water transport is derived as a function of liquid saturation using a pore size distribution (PSD) model PSD functions are derived with parameters that are determined by fitting to the measured total PSD data Computed relations between capillary pressure and liquid maturation for a GDL and a double-lay, red GDL (GDL + MPL) show good agreement with the experimental data and proposed empirical functions To investigate the role of the MPL the relationship between the water withdrawal pressure and liquid saturation are derived for a double-layered GDL Water transport rates and cell voltages were obtained for various feed gas humidity using a two-dimensional cell model and are compared with the experimental results The calculated results for the net drag with application of the capillary pressure derived from the PSD model show good agreement with the experimental values Furthermore the results show that the effect of the MPL on the cell output voltage is significant in the range of high humidity operation (C) 2010 Elsevier B V All rights reserved