The initial stages of polyaniline (PANI) film growth are investigated by a potentiostatic technique. The obtained I-t transients exhibit current maxima which are analyzed for the nucleation type. The evidence is given on two different stages of the nucleation process. It is established that the first stage of growth is a formation of a compact PANI layer which is followed by an additional nucleation process. For that nucleation process it is found that at lower concentrations of aniline monomer 3D progressive nucleation takes place, and with the increasing monomer concentration in perchloric acid solutions 3D instantaneous nucleation prevails. At later stages 1D growth takes place resulting in chain branching. The possibility to observe current maxima, indicating the particular nucleation process, depends on monomer concentration, on the potential of synthesis, and on the counter-ion present, ie on the rate of PANI polymerization. It is shown that clusters resulting from the nucleation process form different shapes depending on the counter-ion present.