The electrocatalytic activity of carbonized polyaniline nanostructures (Carb-nanoPANI) towards oxygen reduction reaction (ORR), estimated in 0.1 mol dm(-3) KOH solution, was significantly improved upon a hydrothermal treatment in 1 mol dm(-3) KOH solution. Namely, the onset of ORR was shifted by similar to 70 mV to more positive potentials, and the number of electrons consumed per O-2 molecule was enhanced in comparison to the original material. The number of electrons involved in ORR depended on loading, and with a loading of 0.5 mg cm(-2), for the potentials lower than 0.5 V vs SCE, the number of electrons approached 4. For this material, high stability of electrochemical behavior and resistance to the poisoning by ethanol was evidenced by potentiodynamic cycling. (C) 2011 Elsevier Ltd. All rights reserved.