The PM1.0 and PM2.5 samples were collected synchronously using a single channel particulate sampler equipped with PM1.0 and PM2.5 cyclones, respectively, and seasonal mass concentration and chemical composition of PM1.0 and PM2.5 were quantified in Seoul and Gwangju in 2021-2022. The mass concentrations of PM1.0 and PM2.5 were 17±11 and 22±14 μg/m3 in Seoul, and 16±9 and 19±12 μg/m3 in Gwangju, respectively. The average ratios of PM1.0/PM2.5 were 83±16% in Seoul and 83±7% in Gwangju. The chemical compositions of PM1.0 and PM2.5 were similar at both sites with OC component being the most dominant, and NO3- increasing from summer to winter, while, the difference of chemical distribution at the two sites was most distinct in the autumn. Gwangju showed a higher proportion of OC and a lower proportion of NO3- compared to Seoul during the autumn. Both sites appear to reflect their urban characteristics, with Gwangju also reflecting the impact of biomass combustion as a part of rural activities.