Binary molecular diffusion and pressure-driven fluxes of gas in porous media are studied. A 2-dimensional model of gas transport in porous media is developed in the field of nonzero gradients of pressure and concentration. Spatial distributions of oxygen concentration and fluxes in a porous diffuser are analyzed for geometric and physical parameters of the electrode. A three-dimensional generalization of the model is performed. Application to oxygen-flow modeling in electrodes of polymer electrolyte fuel cells (PEFC) is discussed for two simple configurations of gas supply channels: serpentine and interdigitated. Comparison of the results obtained for the two configurations is carried out. Oxygen flux through the catalytic membrane plane is investigated for physical characteristics of gases and the diffuser, geometry of the gas supply channels, and gas pressure in them. Recommendations for an optimal pressure regime for the specific geometry of the system and its physical characteristics are given.