A polymer electrolyte fuel cell membrane electrode assembly (PEFC MEA) model that focuses on the structural and reaction parameters of catalyst layers has been developed. The reaction and structural parameters were modeled independently by considering the oxygen reduction reaction (ORR) activity in terms of current per unit active surface area of Pt [A cm(-2)-Pt]. The catalyst layer models were constructed based on an assumption of cylindrical secondary pore structure, which was verified by measuring the primary pore size using mercury porosimetry. We found that penetration of Nafion electrolyte into the primary pores of Pt/C catalysts was restricted, and thus diffusion and reaction in primary pores became negligible. Moreover, the experimental results demonstrated that for the same catalyst, ORR activity remained almost constant, irrespective of the agglomerate size (i.e., 2.7 x 10(-6) A cm(-2)-Pt at 60 degrees C for Pt/C TEC10E50E in this study). This supported our idea that reaction parameters and structural parameters should be considered independently in PEFC modeling. The cell performance predicted with the developed model was satisfactorily accurate as compared to that obtained from experiments. As a result, the modeling developed in this study can be used to construct simple PEFC models that yield results with good accuracy and can be a useful tool for the development of PEFCs in future.