In the preparation of electrodes for the proton exchange membrane (PEMFC), the effect of the fabrication method and the thickness of the gas diffusion layer and the impregnation method of Nation solution on the cell performance was investigated, and unit cell tests were performed. The gas diffusion layer was prepared by rolling, spraying, and screen printing methods, and Nafion solution was impregnated using spraying and brushing methods. The diffusion layer in a PEMFC consists of a thin layer of carbon black mixed with polytetrafluoroethylene (PTFE) that is coated onto a sheet of macro-porous carbon backing cloth. The effects of different fabrication methods and thicknesses of gas diffusion layer are discussed in the light of porosimetry and I-V polarization curves and variables related to the electrode analyzed by numerical simulation. The spraying method proved to be more profitable for cell performance than the brushing method for the impregnation of Nafion solution because it reduced the charge transfer resistance and extended the three-phase region. The goals of this work are to find the optimum thickness of the gas diffusion layer and to undertake an analysis of the system. (C) 2004 Elsevier B.V. All rights reserved.