A deep understanding of the behavior of microstructural parameters in proton exchange fuel cells (PEFCs) will help to reduce the material cost and to predict the performance of the device at cell scale. Changes in morphological configuration, that is, fiber diameter and fiber orientation, of the gas diffusion layers (GDLs) result in variations of fluid behavior throughout the layer, and therefore, the microstructural parameters are affected. The aim of this study is to analyze, for three selected fiber diameters and different percentage presence of inclined fibers, the behavior of the different microstructural parameters of the GDLs. This study is carried out over digitally created two-dimensional GDL models, in which the fluid behavior is obtained by means of the lattice Boltzmann method. Once the fluid behavior is determined, the microstructural parameters, that is, the porosity, gas-phase tortuosity, obstruction factor, through-plane permeability, and inertial coefficient, are computed. Several relationships are found to predict the behavior of such parameters as function of the fiber diameter, presence of inclined rods, or porosity. The results presented in this work are compared and validated by previous theoretical and experimental studies found in the literature. Copyright (c) 2016 John Wiley & Sons, Ltd.