In this paper, the spatio-temporal distribution characteristics of nitrogen dioxide (NO₂) were investigated using data obtained routinely from air quality monitoring stations located in seven major cities and nine provinces in Korea for the period 1998 to 2003. The results indicate that annual trends in NO₂ concentrations generally reflect changes in environmental conditions, while exhibiting cyclic and systematic patterns across seasons. Its wintertime concentrations were most prominent, with concentrations decreasing gradually across spring, fall, and summer. If concentration patterns are examined among different cities and/or provinces, the highest mean values were found from the Capital city, Seoul (34.7 ppb) and the surrounding province, Gyunggi (30.2 ppb). In contrast, remarkably reduced NO₂ concentrations were seen in such regions as the remote island, Jeju and Jeonnam province with mean values of 17.5 and 16.5 ppb, respectively. The overall results of our study indicate that there are strong geographical gradients in NO₂ distributions to exhibit strongly polluted patterns consistently in densely populated urban areas (e.g., major city), compared to large rural areas (e.g., province).