Carbon nanotubes (CNTs), modified with manganese dioxide, were synthesized. Manganese dioxide was obtained by reduction of solution of potassium permanganate with formic acid solution or with carbon of nanotubes. Electrochemical characteristics of the oxygen electrodes containing manganese dioxide modified nanotubes in active layer were investigated. It was shown, that deposition of manganese dioxide on surface of carbon nanotubes results in improvement of electrochemical characteristics in comparison with manganese dioxide as a separate phase. The optimum mass content of manganese dioxide is 50% from the sum (carbon nanotubes+MnO2).