As the Seoul metropolitan city has the largest numbers of population and vehicles, the citizens can be exposed to hazardous air pollutants (HAPs) mainly from the vehicular exhaust and human activities. In this study, we proposed a systematic method for the selection of priority monitoring areas for HAPs using Geographic Information System (GIS). First, emission parameters (emission data, vehicle registration, monitoring data, and so on) and population parameters (population and population density) were plotted using the inverse distance weighted (IDW) interpolation. Then, the interpolation data for individual parameters, which were normalized between 1 and 5 points, were compiled for 270 grids with a resolution of 2 km×2 km. The total score of each grid was calculated using weights (1~5) for the individual parameters. The final ranking of each grid was assigned by four scenarios with varying fractions of the emission and population parameters from 50 : 50 to 80 : 20. Consequently, nine grids were suggested as priority monitoring areas, and all of them are located in the southwestern part of Seoul.