The optical transitions and charge transport in. electrochromic polyaniline films have been studied by the impedance and spectroelectrochemical methods in aqueous and organic electrolytes containing proton acid. By means of impedance spectroscopy, the electron diffusion coefficients across the film for anode and cathode processes have been measured. It has been found that the higher rate of electron transport in the bleaching (cathode) process in comparison with the Coloration (anode) process may be related to the conformation rebuilding of conducting polymer chains.