Ordered mesoporous carbon (OMC) with highly ordered pore channels was applied as an oxygen-side electrode for a Li-O2 battery. To evaluate the effect of the pore channel size on battery performance, we employed OMCs possessing two different pore sizes (6 and 17 nm). When cycled at a current density of 200 mA g(-1)carbon, the OMC electrodes reduced polarization in the oxygen evolution reaction by 0.1 V compared to those consisting of conventional super P carbon electrode. X-ray diffraction and transmission electron microscopy of the discharged oxygen electrodes provided evidence for the formation of amorphous Li2O2, a product of the oxygen reduction reaction, inside the OMC pores rather than on the electrode surface as in the case of the super P electrode. The OMC electrodes were also effective at high current densities (500 mA g(-1)carbon and 1000 mA g(-1)carbon).