During the past decade, particle size distributions of atmospheric aerosols have been studied extensively due to the confirmed influence of aerosol on global climate, atmospheric visibility and human health. Campaings carried out at clean or backroung stations are important because the influece of major anthropogenic aerosol sources connected to industry, transport and large cities is suppressed. Therefore, results obtained at these cites can help us better understand the underlying principles of aerosol physic and chemistry. In the Czech republic, one of the stations suitable for rural atmospheric aerosol monitoring is the Košetice Observatory.