The purpose of this study is to extract the main locational factors to affect the location of fastfood stores in Kangnam -Gu, Seoul by using Geographic Information Systems. The Franchise system, which came to be employed in full scale since 1990, now enjoying the booming period, especially fast food industry. The procedure of this research has four steps. First, the spatial distribution of fastfood chain stores in Seoul is analyzed by the land use and road map. Second, the spatial variations of fastfood stores in dong districts of Seoul is explained by multiple regression analysis. Third, the main locational factors to affect the location of fast food stores in Kangnam -Gu are extracted by demand and supply sides using GIS technologies. Finally, the potentiallocational zones where are selected by extracted locational factors are compared with the actual distribution of f astf ood stores in Kangnam - Gu. In terms of demand side, the main locational factors include commercial and service facilities, sub¬ways and bus stops which have a lot of pedestrians, and large apartment districts that have high popu¬lation densities. In terms of supply sides, the main locational factors include land use types and land value, accessibility. After fast food chain stores of Kangnam -Gu are overlaid final potentiallocational zones extracted by demand and supply sides of locational factors, it can be identified that over 80 % of fastfood stores are located in the potentiallocational zone. In conclusion, this study shows that spatial analysis functions may potentially be improved using GIS technologies. However there are still difficulties for the locational analysis for service industries to col¬lect appropriate data in terms of computerized base maps as well as consumer behavior and store characteristics itself.