Nafion (perfluorinated ion-exchange membrane) films allow the transport of counterions from the solution to the PB film necessary during the reduction and oxidation processes to maintain the film electroneutrality. Nafion films cause a decrease in the apparent diffusion coefficient. This apparent diffusion coefficient could be interpreted as a measurement of counterions transport through films. Prussian blue films stability is increased by the presence of Nafion films allowing the study of the electrochemical behaviour of the oxidized form of Prussian blue films (Berlin green, Prussian yellow) by impedance spectroscopy.