Poly(N-vinylcarbazole) (PVCz) films were prepared by potentiostatic deposition onto indium tin oxide-coated glass (ITO) electrodes from acetonitrile solutions containing the monomer. Two different supporting electrolyte solutions, LiClO4 and LiBF4, were used. The electrochemical behaviour of the polymer-coated electrodes was studied in solutions containing successively, both electrolytes, by means of in situ W-vis spectrophotometry. The experimental results obtained in both electrolytes at the same analytical concentration could not be interpreted completely by considering only the influence of the size of the electrolyte anion. Spectroelectrochemical measurements performed in electrolyte solutions of the same conductivity have shown the importance of the specific interactions which may exist between the anions and the oxidised polymer sites.