• Carbon sequestration in forest ecosystems is an important though still uncertain process in the global greenhouse gas balance. • We computed biomass organic carbon (BOC) stocks of spatially explicit forested landscape units (LSU) in Belgium based on data collected in the regional forest inventories of 1984 (Wallonia region only) and 2000 (Wallonia and Flanders). C stock changes between 1984 and 2000 were estimated for Wallonia. • The total BOC pool stored in Belgian forests in 2000 amounts to 57.8 Mt C in 6 222 km 2 , or 10.0 kg C m −2 in broadleaf, 9.5 kg C m −2 in coniferous and 8.7 kg C m −2 in mixed forest. Based on previous soil organic carbon (SOC) analysis for the same LSU, BOC and SOC stock per LSU appeared only weakly correlated. The total BOC sequestration between 1984 and 2000 equals 5.7 Mt C over an area of 5 107 km 2 , resulting in a flux of 0.07 kg Cm −2 y −1 . The BOC content of broadleaf forest in Wallonia increased with 6%, of coniferous forest with 32% and of mixed forest with 11%. • The observed regional differences in BOC stocks and in BOC sequestration rates are explained by the forest age-class distribution and site productivity. The strength of the spatially explicit approach lies in the fact that BOC and SOC data originating from diverse sampling strategies can be combined for spatial or temporal comparison of C stocks. forest inventory / Belgium / forest biomass / soil / carbon sequestration