In the recent literature the influence of lean fuel, type of fuel, velocity profile and the flow direction on the performance operation of solid oxide cells (SOCs) is commonly investigated. SOCs operate at elevated temperature, typically above 600°C. They consist of several layers including two porous electrodes which are separated by gas-tight electrolyte. SOCs generate electricity when operated in fuel cell mode (SOFC – Solid Oxide Fuel Cell) or produce hydrogen in electrolysis mode (SOEC – Solid Oxide Electrolyzer Cell). The typical porosity of anode (fuel electrode in SOFC mode) varies in the range from 20% up to 40% (after sintering process). The value of porosity may limit the mass transport and the overall performance of SOC. Within this work, the diffusion mechanism in porous electrode was investigated computationally and experimentally. A set of mass transport models (Fick laws, modified Fick law, Maxwell-Stefan Model, Dusty Gas Model), which are used for modelling of SOCs, were analyzed. They were thoroughly described and discussed in order to demonstrate their similarity and differences, advantages, disadvantages and restrictions in usage. Finally, a detailed computational fluid dynamic (CFD) model of the diffusive transport in porous electrode was elaborated in order to determine the influence of temperature and the significant concentration gradients of gas components on the mass transport in porous medium, like SOC’s electrode. The developed model was validated using experimental data collected at Institute of Power Engineering. Laboratory investigations followed by the numerical studies were performed using anode supported SOC, fabricated in the Institute of Power Engineering in Poland. Comprehensive analysis of specific operating conditions allows the elaboration of the list of guidelines and parameters which can enhance gas diffusion at high temperature and in the regime of significant concentration gradients of gas components. Results of analysis and models review summarize the best approaches to model the mass transfer processes in high temperature membranes, separators, selective sieves or porous filters.