Indoor air quality can be affected by indoor sources, ventilation, decay, and outdoor levels. Various indoor and outdoor combustion sources make nitrogen dioxide (NO₂), which is a by-product of high temperature fossil fuel combustion. Especially, the presence of gas ranges and smoking has been identified as one of the major factors contributing to indoor NO₂ exposures. In this study, we assessed the personal exposure to NO₂ with measurements of indoor and outdoor NO₂ levels in residence, house characteristics, and questionnaire, comparing the industrial complex area with country area. Personal exposure concentrations were significantly correlated with indoor NO₂ concentrations of residence in both industrial complex area and country area with correlation coefficients of 0.561 and 0.664, respectively, comparing to outdoors. According to multiple regression analysis, indoor NO₂ levels in residence could be only affected by outdoor levels (p=0.000) in spite of higher indoor source such as smoking indoors . Therefore, it is suggested that outdoor air quality as well as indoor air quality should be considered to reduce the personal exposure to air pollutants.