C-60 fullerene film modified electrodes were investigated for the electrochemical reactions of cytochrome c, It was established, that depending on the oxidation state of the fullerene films, the electrochemistry of the protein varied. The best, stablest redox reaction could be measured on partially reduced film. The response of cytochrome c was quite independent of the underlying substrate (gold or glassy carbon), indicating that the fullerene film acted as a promoter. Molecular sieve character and the possible effect of negative charges or polar groups on the surface of the films were suggested to be the reason of enhanced stability of the electrochemical response compared to bare electrodes.