Commonly available Korean pine (Pinus korariensis) and Mongolian oak (Quercus mongolica) were used as biomonitors to find out the background air concentrations of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in Seoul metropolitan area in Korea. Needles and leaves were collected in February, April, August, October and December in the year 2002 from the city center (Namsan) and outskirts (Kwanaksan) of Seoul. The annual average concentrations (dry weight) of PCBs and PBDEs were higher in the city center than outskirts and in Mongolian oak than pine leaves. Those values in Mongolian oak were: Namsan PCBs 7.58±6.73, PBDEs 1.80±2.07: Kwanaksan PCBs 6.77±4.08, PBDEs 0.70±0.55. The corresponding values in pine needles were: 2.68±0.92, 0.70±0.41 ∶ 2.3±1.61, 0.22±0.18. Overall 24 PCBs, including dioxin-like coplanar PCBs and 9 PBDEs congeners were detected in the samples. Concentrations were usually high in winter than summer. Pine needles enriched mostly lower chlorinated PCBs and Mongolian leaves the higher chlorinated congeners. The most dominant PBDEs determined in both species were BDE-99 and −47. Correlation of PCB concentrations with gas partition coefficient (Kp) and octanol water partitioning coefficient revealed that the uptake mechanism in pine needle was governed by absorption from vapor phase and aerosol particle adsorption in Mongolian leaves. Correlation between PCBs and PBDEs suggests different point sources. TEQs were derived for toxic PCBs in leaf samples as an indicator of possible air-borne health risk.