The catalytic influence of polyaniline (PANI) film, prepared from sulphuric and perchloric acid solutions, on hydroquinone/benzoquinone benzoquinone (HQ/BQ) and Fe-2+/3+ reactions has been investigated. The effect of the PANI layer thickness on redox reactions has been established, as well as different kinetics depending on the counter-ion incorporated. The location of the reactions taking place is discussed. Evidence is given for metal-like behaviour of PANI at potentials of emeraldine existence and redox-polymer behaviour at potentials of pernigraniline existence.