The low exhaust gas temperature of vehicles in the urban driving cycle is a major cause of air pollution in the Seoul Metropolitan Area, due to the common stop-and-go driving style. We herein investigated the emission characteristics of regulated (NOx, PM, CO, nonmethane hydrocarbons (NMHC)) and unregulated (volatile organic compounds (VOCs), aldehydes, polycyclic aromatic hydrocarbons (PAHs)) air pollutants for heavy duty diesel trucks and buses equipped with different after-treatment systems (diesel particulate filter (DPF)+exhaust gas recirculation (EGR) and selective catalytic reduction (SCR)) under urban driving cycle. The NOx emissions depended on the combustion and working temperatures of the SCR catalysts, and the PM emissions were found to be low. Alkane groups dominated the nonmethane volatile organic compounds (NMVOCs) emissions, with 43-59% of these emissions resulting from the low efficiency of the oxidation catalyst toward alkane emissions. The chemical components of the NMVOCs emissions were found to be influenced by the after-treatment systems and the engine start conditions due to incomplete combustion and the evaporation of liquid fuel. Formaldehyde comprised the largest portion of the aldehydes and PAHs emissions remained largely undetected. In addition, formaldehyde was the major NMHC component, ranging in adundance from 14 to 29%. These results will therefore be expected to aid in establishing a system for calculating hazardous vehicle air pollutants emissions in Korea.