This paper reports cyclic voltammograms of cytochrome c on recessed nanodisk-array electrodes (RNEs) based on nanoporous films (11, 14 or 24 nm in average pore diameter: 30 nm thick) derived from polystyrene-poly(methylmethacrylate) diblock copolymers. The faradic current of cytochrome c was observed on RNEs, indicating the penetration of cytochrome c (hydrodynamic diameter approximate to 4 nm) through the nanopores to the underlying electrodes. The faradic current on RNEs with 11- and 14-nm nanopores mainly originated from cytochrome c adsorbed on the underlying electrodes, whereas the current on RNEs with 24-nm pores was diffusion-controlled. Interestingly, the diffusion-controlled current of cytochrome c was significantly smaller than that estimated from the faradic current of 1,1'-ferrocenedimethanol on the RNEs. The smaller faradic current suggested more effective decrease in the diffusion coefficient of cytochrome c as compared to that of 1,1'-ferrocenedimethanol, which probably reflected enhanced steric and chemical interactions within the nanopores. Comparison between experimental data and results of finite-element computer simulations made it possible to assess the structure of the nanoporous films and the diffusion coefficients of redox species within the nanopores. (C) 2011 Elsevier Ltd. All rights reserved.