This study quantified $CO_2$, SO$_2$and NO$_2$uptake by vegetation for the Namsan Nature Park in Seoul, and explored values for the park to contribute to atmospheric purification. Broad-leaved forest accounted for about 54% of total forest area, and tree-age structure was dominated by a young, growing tree population. Tree density and basal area averaged 17.5 trees/100$m^2$ and 2,580$ extrm{cm}^2$/100$m^2$, respectively. Atmospheric purification per unit area by forest type and age class was greater in older age classes, associated with changes in basal area, and tended to be greater in broad-leaved or mixed forest than in coniferous forest for the same age classes. Mean $CO_2$storage per unit area for all the forest types and age classes was 293.8 t/ha and economic value of the $CO_2$storage was ￦ 147millions/ha. Annual uptake averaged 24.6t/ha/yr for $CO_2$, 17.1 kg/ha/yr for SO$_2$and 43.9 kg/ha/yr for NO$_2$, and economic value of the annual uptake was ￦ 13millions/ha/yr. Total forest area stored 72,100 t of $CO_2$, and annually sequestered 6,040 t/yr of $CO_2$, 4,200 kg/yr of SO$_2$and 10,770 kg/yr of NO$_2$. Economic value of atmospheric purification for the entire area amounted to approximately ￦ 36,100millions for the $CO_2$storage, and ￦ 3,100millions/yr for the annual $CO_2$, SO$_2$ and NO$_2$uptake. The park played an important role through annually offsetting $CO_2$emissions from fossil fuel consumption by 1,100 persons, SO$_2$emissions by 2,800 persons, and NO$_2$ emissions by 1,160 persons. The results from this study are expected to be useful not merely in informing the public of atmospheric purification values of urban nature parks, but in urging the necessity for replanting and management budgets.