Accumulation of carbon (C) in biomass and soil, and using forest residues for bioenergy are examples of forestry's contribution to reducing the enhanced concentration of greenhouse gases in the atmosphere. The aim of this report was to study the effect of rotation length on carbon accumulation in biomass and soil, and on the amount of forest residues that could substitute fossil fuel during 2000-2100. Two models, based on inventory data from the Swedish National Forest Inventory, were used to simulate the effects of a changed rotation length in the region of Dalarna (1.8×106 ha), in central Sweden. During the studied period, the accumulation of carbon in biomass was 32 kg C ha−1 yr−1 larger for the prolonged rotation period and 105 kg C ha−1 yr−1 smaller for the shortened rotation period compared with the base scenario. The build-up of carbon in forest soil was 23 kg C ha−1 yr−1 larger for the prolonged rotation than for the base scenario, whereas the shortened rotation was 24 kg C ha−1 yr−1 smaller than the base scenario. The potential to substitute fossil fuel was 37 kg C ha−1 yr−1 larger for the shortened rotation and 17 kg C ha−1 yr−1 smaller for the prolonged rotation compared with the base scenario. The annual accumulation of carbon in biomass decreased in all scenarios, which resulted in a prolonged rotation scenario possibly being a poor long-term solution (>100 yrs). The amount of forest residues that could substitute fossil fuel increased in all scenarios during the studied period.