The electrochemical behaviors of porous mixed conducting cathodes for solid oxide fuel cells have been quantitatively investigated in this paper through numerical simulations on 1D and 2D porous models by using analytical approach and finite element method. A clear and comprehensive picture about the cathode overpotentials and current density distributions has been revealed as a convoluted function of cathode's oxygen surface reaction kinetic rate constant, ionic bulk conductivity, geometric size and pore structures. On the basis of simulation results, extended discussions were also made on the impacts of structural heterogeneities including the pores and the graded interfacial structure composed of a single phase and dual phases in the area bordering electrolytes on the effective cathode areal resistance that may be adopted to characterize the electrochemical behavior of cathodes. (C) 2004 Elsevier B.V. All rights reserved.