Modeling morphological and hydraulic properties of thin porous media, such as filter layers and papers is highly relevant to various industries. In our previous studies, the X-ray tomography and FIB-SEM methods were applied to capture micro- and nano-scale pores in uncoated paper and coated layer, respectively. Here, the reconstructed pore structures were used to investigate two-phase water imbibition in these porous media. The obtained pore size distributions showed a log-normal probability density function. Such a distribution, together with concepts from critical path analysis and percolation theory, was applied to calculate relative permeability over a wide range of water saturations. Comparison with pore-scale numerical simulations showed the capability of this method to estimate water relative permeability for coated and uncoated papers. (C) 2018 Elsevier Ltd. All rights reserved.