An electrochemical method for the preparation of thin films of the Na+-containing Prussian Blue, NaFeIII[Fe-II(CN)(6)] . nH(2)O, is proposed. The system has been studied electrochemically in sodium and potassium electrolytes, as well as in solid-state, ie in the absence of contact with any liquid electrolyte phase. Hydrated-Na+ counterions are sufficiently mobile in NaFe[Fe(CN)(6)] to support the system’s redox reactions. During voltammetric experiments in aqueous potassium solutions, structural Na+ cations in the film are irreversibly replaced by smaller hydrated-K+, and the material undergoes reorganization to the commonly studied potassium-containing analogue, KFeIII [Fe-II(CN)(6)]. The films have been analyzed using scanning electron microscopy equipped with X-ray fluorescence elemental analysis probe. Structural differences between NaFe[Fe(CN)](6) and KFe[Fe(CN)(6)] are apparent from X-ray absorption fine structure spectroscopy and ir measurements. A comparison is also made to so-called "insoluble" Prussian Blue, Fe-4(III)[Fe-II(CN)(6)](3).