In this paper, a mathematical simulation model is proposed to describe the water transport in proton conductive membranes, used in polymer electrolyte fuel cells (PEFCs). The model, which includes the calculation of electrochemical parameters of a PEFC, represents a quite innovative approach. In fact, it is based on the use of original mathematical relationships taking into account diffusional and ohmic overpotentials for electrode flooding and membrane dehydration problems. The calculated performance of polymer fuel cells using a Nafion 117 membrane clearly demonstrates the model validation (+/-3% variation with respect to experimental data). Besides, analysis of model results allows a useful comparison of two different membranes (Nafion 117, Dow) in order to define the best membrane/electrode assembly.