Complex measurements of size distributions and chemical content of aerosols, trace gases SO2, NH3, ozone, and meteorological parameters were performed in boreal forests of Central Siberia during 03.2005ndash;05.2006 at the rural station of Listvyanka. The data from Listvyanka are then analyzed from the point of view of their similarities and differences with respective data at Hyyti#xE4;l#xE4; background station Southern Finland. The goal of this paper is to compare the conditions of formation of secondary aerosol particles in boreal forests in two different regions: in Southern Finland Hyyti#xE4;l#xE4; station and Siberia Listvyanka station. Our main conclusion is that the particle formationndash;growth processes in Listvyanka occur in presence of high compared to Hyyti#xE4;l#xE4; concentrations of sulfur dioxide and ammonia. We show that their concentrations are enough for providing the particle growth up to 3.5nbsp;nm h-1 with much higher concentration of the nucleation mode particles in contrast to Hyyti#xE4;l#xE4;, where the sulfuric compounds are much less concentrated and the nucleation mode particles grow by consuming low volatile organic vapors that result from photochemical processing of highly volatile organic plant emissions. On the other hand, the nucleation bursts in Siberia occur more seldom than in Hyyti#xE4;l#xE4;. The difference in UVB irradiation regimes at Siberian stations and in Hyyti#xE4;l#xE4; can lead to different seasonal patterns of the particle formationndash;growth rates and the concentrations of nucleation mode in Siberia.