The electrocatalytic reduction of oxygen at electropolymerized films of a number of different manganese, iron and cobalt porphyrins supported on multi-walled carbon nanotubes (MW-CNTs) which have been pre-stabilized with ultra-thin layers of organic 4-(pyrrole-1-yl) benzoic acid (PyBA) is reported. Special emphasis has been on the multiple oxidation states of manganese as central metal ion and its potential advantages for the electron transfer process during the reduction of molecular oxygen in a 0.1 M phosphate buffer solution. Electropolymerization of metal porphyrins leads to catalytically active films on the electrode. The incorporation of MW-CNTs in the film leads to a significant decrease in the hydrogen peroxide produced during the oxygen reduction reaction (ORR) and a significant positive shift of the oxygen reduction potential. Of the complexes studied, manganese tetratolyl porphyrin (MnTTP) has shown the best activity and stability towards oxygen reduction. (C) 2008 Elsevier Ltd. All rights reserved.