Indoor air quality tends to be the dominant contributor to personal exposure, because most people spend over 80% of their time indoors. In this study, indoor and outdoor NO2 concentrations were measured with simultaneously personal exposures of 30 university students in weekday and weekend in Daegu, Korea. House characteristics and subject\'s activity pattern were used to determine the effects on personal exposure. Since university students spent most of their times indoor, their NO2 exposure were associated with indoor NO2 level during both weekday and weekend in spite of different time activity. Using time-weighted average model, NO2 exposures of university students were estimated by NO2 measurements in indoor home, indoor school, and outdoor home. In conclusion, major personal exposure to NO2 resulted from air quality of indoor environment at house. Keywords：Nitrogen Dioxide, Personal Exposure, Time-Weighted Average, Time Activity