In this study, we compare new particle formation (NPF) in the boundary layer at different sites in Europe: Melpitz, Germany (central Europe), San Pietro Capofiume, Italy (southern Europe) and Hyytiala, Finland (northern Europe) for the period of two years (July 2003-June 2005). NPF was studied based on observations of the particle size distribution, meteorological and gas-phase parameters. Nucleation was found to occur frequently at all stations, however seasonal differences were observed for every station. These differences have a clear correlation with the annual variation of estimated formation rate values. The growth rate reached its maximum values during summer at all three stations. In Hyytiala the formation and growth of the particles was characterized by low pre-existing condensation sink and most likely high biogenic VOC concentrations associated with the growth season, and in Melpitz and San Pietro Capofiume by the high level of pollution arriving from the nearby industrial and agricultural sources.