A long term (1989-1999) investigation has been made using the cloud-to-ground (CG) lightning flash data collected to study the aerosol effect on lightning activity over five major urban areas of South Korea. The cloud-to-ground (CG) lightning data were collected from the Korean Meteorological Administration (KMA) of South Korea. The results reveal that an enhancement of around 40-64% in the negative flash density and 26-49% in the positive flash density is observed over the urban areas compared to their surroundings. On the other hand a percentage decrease of around 7-19% in positive flashes occurs over the urban area. The results are in good agreement with those available in the literature. The enhancement of lightning is examined in relation to the PM10 (particulate matter with aerodynamic diameter smaller than 10 μm) and SO2 concentrations. The PM10 and SO2 concentrations exhibit a positive linear correlation with the number of cloud-to-ground flashes, while a negative correlation is observed between those concentrations and the percentage of positive flashes. Positive correlations of 0.795 and 0.801 are found for the PM10 and SO2 concentrations, respectively, when compared separately with the number of CG flashes, establishing the effect of aerosols on urban CG lightning enhancement. However, negative correlations of - 0.577 and - 0.548 are obtained for the PM10 and SO2 concentrations, respectively, when compared separately with the percentage of positive flashes.