Net Ecosystem Carbon Balance (NECB) of Russian forests for 2007–2009 is presented based on consistent application of applied systems analysis and modern information technologies. Use of landscape-ecosystem approach resulted in the NECB at 546±120 Tg C year–1, or 66±15 g C m–2 year–1. There is a substantial difference between the NECB of European and Asian parts, as well as the clear zonal gradients within these geographical regions. While the total carbon sink is high, large forest areas, particularly on permafrost, serve as a carbon source. The ratio between net primary production and soil heterotrophic respiration, together with natural and human-induced disturbances are major drivers of the magnitude and spatial distribution of the NECB of forest ecosystems. Using the Bayesian approach, mutual constraints of results that are obtained by independent methods enable to decrease uncertainties of the final result.