A performance analysis of a proton exchange membrane fuel cell is reported in this work. Two different flow patterns are modeled as gas distributors and current collectors of a PEM fuel cell. Both flow patterns have the same active area with similar channel distribution over the membrane electrode assembly. Three dimensional models are used in order to simulate the performance of the fuel cells. The Navier-Stokes equations as well as potential fields (potentiostatic and galvanostatic) are solved using computational fluid dynamics techniques. Two dimensionless parameters were computed to quantify and compare the uniformity of the flow over the reaction area. The present analysis shows that achieving a good flow distribution is a key parameter in the PEMFC performance. The reduction of the concentration losses is the main result when a parallel channel configuration operates with uniform reactants distribution. In this study is demonstrated that the conventional parallel channels flow pattern does not achieve similar flow conditions in each sub-stream and therefore, irregular energy generation is obtained.Copyright © 2010 by ASME