An electrostatic self-assembly process based on layer-by-layer deposition was employed to prepare thin films of charged polyaniline (PANI) and two polyanions: poly(styrene sulphonate) (PSSA) and an 18-base oligonucleotide (ON). The concentrations of polyion depositing solutions were varied and the effect on the thin films' properties was examined. The layer-by-layer deposition was monitored by means of UV-Vis spectroscopy, and it was shown that in all investigated cases the deposition of bilayers is linear in respect to the number of deposited bilayers. The UV-Vis results confirmed that ONs easily incorporate into PANFON films. Cyclic voltammetry experiments revealed different electrochemical behaviour of PANI/PSSA and PANYON films, with PANI/ON films showing less electroactivity. Scanning Electron Microscopy analysis showed significantly different morphology of those films. (c) 2005 Elsevier B.V. All rights reserved.