In this work a manganese oxide dispersed on a high surface area carbon powder at two ratios (Mn y O x /C) was evaluated as catalyst for the oxygen reduction reaction (ORR) in alkaline solutions. An impregnation method was used to prepare the catalysts, starting from a manganese nitrate precursor solution containing the carbon powder (Vulcan XC-72). A thin porous coating rotating disk electrode was employed to collect the experimental ORR polarization data and the results obtained were analyzed with the application of the flooded-agglomerate/thin film model for the catalyst layer. Results indicated that the reaction is sensitive to the manganese oxide to carbon ratio on the catalyst. The catalyst containing lower Mn y O x /C ratio tended to follow the peroxide pathway (2e− mechanism) forming peroxide ions. When the Mn y O x content is increased the complete reduction of oxygen to hydroxide ions pathway (the 4e− mechanism) takes place into some extent at low potentials due to the occurrence of a catalytic disproportionation of HO2 −.