This study has been carried out to estimate carbon contents in an average 40-years-old Pinus koraiensis plantations and an average 37-years-old Larix leptolepis plantations in Gongju, Chungnam Province. Average carbon concentration in stemwood, stembark, branches, needles, and root were 54.31% in Pinus koraiensis and 53.49% in Larix leptolepis stands. Carbon contents was estimated by the equation model logWt=A+BlogD where Wt is oven-dry weight in kg and D is DBH in cm. Total carbon contents was 103.38tC/ha in Pinus koraiensis stands and 96.59tC/ha in Larix leptolepis stands. Net primary carbon production was estimated at 8.79tC/ha/yr in Pinus koraiensis stands and 11.42tC/ha/yr in Larix leptolepis stands.