The polarization resistances in solid oxide fuel cells are predicted using the cell combined micro- and macro-model; and the effect of the micro-/nano-structure of porous composite electrodes on the cell total polarization resistance is studied. In this study, several anode-supported co-flow planar Ni–YSZ/YSZ/LSM–YSZ cells with a range of micro-/nano-structures of electrodes are simulated; and the mean total polarization resistance and mean polarization resistances corresponding to the anode, cathode, electrolyte, and interconnect of these cells are predicted. The results reveal that there is an optimum value for most of the structural variables of porous composite electrodes at which the mean total polarization resistance of the cell is minimized.