Open-cell polyurethane foams have been investigated for various filtration applications to treat industrial byproducts and waste water. Flow-related morphological characterization of three types of polyurethane foams: (1) control, unmodified polyurethane foam, (2) flexible polyurethane foam obtained by chain extension, and (3) rigid polyurethane foam obtained by chain extension, is presented in this study. Analysis of micrographs, using histograms based on pore size, revealed that the pore size varied in the foams based on their composition. The permeability (K) of the foams for liquid flow, measured by a falling-head permeameter was in the range of 0.45 × 10⁻¹¹–2.62 × 10⁻¹¹ m². In comparison to the theoretical permeability models, the experimental values were smaller by two orders of magnitude. The theoretical prediction of the permeability improved after considering effective porosity and replicated the trend seen in the experiments, but the large gap between the prediction and experiments remained. The failure of the theoretical models points to the need for developing more accurate permeability models after including 3-D pore interconnections and swelling of solid matrix.