A series of oxygen depolarized cathodes (ODC) with different gas diffusion layers (GDLs), determined by different carbon black fillers, PTFE contents, and pore-forming agents, were fabricated. The structure-sensitive activity for the oxygen reduction reaction (ORR) on these cathodes has been studied in alkaline solutions, with the aim of revealing the effect of pore structures in GDLs on the ORR activity. A linear-type gas permeability (K) dependence on the ORR activity is observed, indicating that K is one of the key parameters representative of the ability of gas diffusion through GDLs. The added PTFE as binder favors the formation of the secondary pores instead of the primary pores in GDLs. By introducing (NH4)(2)C2O4 as pore-forming agents in GDL, the best performance of the ODC was obtained. The resulting GDL possessed the average secondary pore diameter of 144 nm and the secondary pore volume of 0.3032 mL/g.