Poly(1,8-diaminocarbazole) (PDACz) films on the Pt electrodes were obtained from acetonitrile (0.1 M LiClO4) and acidic aqueous solutions (0.1 M HClO4). The changes in the shape of polymerization curves in the two media are discussed in terms of a limited conductivity window of the fully oxidized PDACz. The polymer structure of the films obtained from acetonitrile and acidic aqueous solution was proposed on the base of FTIR spectra and the results of theoretical calculations. Density functional theory (DFT) was used to calculate a distribution of unpaired-electron spin density for monomer radical cations to predict the coupling positions during polymerization. This method allowed to resolve the problems concerning the monomer linkage, still present after analysis of FTIR spectra of the polymer. (C) 2009 Elsevier Ltd. All rights reserved.