A pore-network model was developed to study the water transport in hydrophobic gas diffusion layers (GDLs) of polymer electrolyte membrane fuel cells (PEMFCs). The pore structure of GDL materials was modeled as a regular cubic network of pores connected by throats. The governing equations for the two-phase flow in the pore-network were obtained by considering the capillary pressure in the pores, and the entry pressure and viscous pressure drop through the throats. Numerical results showed that the saturation distribution in GDLs maintained a concave shape, indicating the water transport in GDLs was strongly influenced by capillary processes. Parametric studies were also conducted to examine the effects of several geometrical and capillary properties of GDLs on the water transport behavior and the saturation distribution. The proper inlet boundary condition for the liquid water entering GDLs was discussed along with its effects on the saturation distribution. (C) 2008 Elsevier Ltd. All rights reserved.