The impacts of climate change on forest resources during the next century were studied on regional and national scales using a gap-type forest ecosystem model. Computations were made using tree and stand data from 1256 permanent sample plots established in the course of a national forest inventory (NFI) representing forests on mineral soil sites in Finland. It was assumed that mean annual temperature would rise by 1-6°C and annual mean precipitation by 2.5-15% within a century. The results produced by the simulations indicated that prevailing forest management practices in Finland would, under the current climate, lead to balanced forest development and that the growing stock would increase by about 7% in southern Finland and 80% in northern Finland when compared to the initial conditions. Under changing climatic conditions during the next century, the growing stock in southern Finland will decrease with fewer conifers and more Pendula birch. In northern Finland, the growing stock at the end of the simulation was ca. 30% greater than the growing stock under current climate. In a changed climate, almost half of Finland's forest resources will be located in northern Finland at the end of next century.