This study investigates the gas permeability, bulk density, thickness and conductivity of two types of gas diffusion layer (OC14, NC14) as a function of the compressed thickness. The compression of a gas diffusion layer reduces gas permeability and contact resistance. The performance is measured using a single proton exchange membrane fuel cell (PEMFC) with an active area of 25 cm(2). The results provide an optimum value of compression ratio that maximizes the cell performance. For OC14 the optimum compression ratio is about 64%, whereas for NC14 it is 59%. The best performances are 375 mA/cm(2) and 296 mA/cm(2) at 0.7 V, respectively. These results concerning the balance between compression and performance provide vital information for the fabrication of stacks and support for industrial applications. (C) 2008 Elsevier Ltd. All rights reserved.