Introduction Health effects of particulate matter (PM) could differ by individual characteristics, however, the modifying effects are inconsistent across previous studies. Finding susceptible population is important for explaining regional and temporal variation in PM risk. The objective of the study is to investigate individual susceptibility factors to PM related mortality in Seoul, Korea, 1998-2012. Methods Using a generalized additive model adjusted time-trend, we evaluated the association between PM and daily mortality caused by all, cardiovascular and respiratory diseases. Stratified analyses by individual characteristics-sex, age, place of death, occupation, marital status, and education-were conducted to examine the modification effects. We calculated the 95% confidence interval of differences between effect estimates by strata. The strata with mean daily death count under 5 were excluded from the analysis. Results An increase of 10 µg/m3 in daily average concentration of PM10 and PM2.5 was significantly associated with increase in all-cause mortality by 0.18% and 0.17%, respectively. The effects of PM10 on all-cause, cardiovascular, respiratory mortality were higher in elderly and male. In-hospital death, unemployed, married, and highly educated people were more susceptible to PM10 for all-cause mortality than others. For cardiovascular mortality, PM10 risks were higher in out-of-hospital death, those with professional occupation, married, and those with lower education level. Susceptibility pattern of PM2.5 was similar to PM10. Conclusions Our results shown that, depending on the types of disease, risks in PM are different between subpopulations. These findings provide some information about individual susceptibility that may have implications for further health risk assessment of air pollution and local environmental health policies.