The greenhouse impacts of the Finnish forest sector, including the forest biomass, forest industry, forest products in use, foreign trade and waste management are discussed. The main carbon storages and flows are estimated and the greenhouse gas balance both totally and on national level are presented. The history of the greenhouse impact is also estimated and two future scenarios of the forest sector are compared. The present use and potential for additional use of bioenergy is also reviewed, and the impact of expanded bioenergy use on the national CO2 emissions is illustrated with scenario examples.