Water distribution in gas diffusion layers (GDLs) of polymer electrolyte membrane fuel cells (PEMFCs) is determined by the pore morphology of the GDL as well as the flow conditions between the GDL and the gas flow field, where interconnect ribs and gas channels are placed side-by-side. The present study employs a steady state pore network model based on the invasion-percolation (IP) process to investigate the water transport in the under-rib region, in the under-channel region, and in between those regions inside the GDL. The interconnect rib partially blocks the outlet surface of the GDL, which forces water transport paths from the under-rib region to grow towards the gas channel through an extra IP process. The pore network model predicts spatially non-uniform water distributions inside the GDL due to the interconnect ribs, especially with an increased saturation level in the under-rib region. Parametric studies are also conducted to investigate the effects of several geometrical factors, such as width of the rib and the channel, thickness of the GDL, and water intruding condition at the inlet surface of the GDL. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.