Aiming to investigate effects of deforestation on ecosystem carbon dioxide budget in a boreal forest, a long-term flux observation by means of the eddy covariance method was performed over growing seasons from 2001 to 2003 at a mature larch forest and an adjacent experimental cutover near Yakutsk, Russia. Net ecosystem exchange (NEE) of carbon dioxide was negative from June to August at the larch forest and five-month (from May to September) total exchange ranged from -81 to -126 gC m^-2 (5 months)^-1, NEE at the cutover was more than twice as large as NEE at the larch forest. NEE at the cutover decreased year by year, and the daily exchange became negative in short periods in the third year (2003), which is because of absorption by the recovered surface vegetation. Seasonal NEE at the cutover decreased to +87 gC m^-2 (5 months)^-1 in 2003, which indicates a quick recovery of surface vegetation, however, a careful and durable monitoring of the recovery course of ecosystem carbon sequestration in relation to the succession of surface vegetation is indispensable.