This study investigated the integrated effects of family, school, internet, and mass culture factors on the identity formation of adolescents. Specifically, the purposes of this study were to categorize adolescents into groups by what they do during the time except the life in school and to investigate differences among the groups regarding the identity information(body image, self-esteem, self-identity) and the influences of environmental factors on identity formation of adolescent. The study distributed questionnaires to middle and high school adolescents of five representative cities in South Korea. The total respondents were 2240(960 from Seoul/Kyongki, and 320 each from Taegu, Pusan, Kwangju, and Taejon). The response rate was 98.7%. The data were analyzed by factor analysis, cluster analysis, ANOVA, Duncan test, and multiple regression. The results showed that Korean adolescents were segmented into five groups : TV preference group, computer preference group, friends and family involvement group, homework and study preference group, and study institute involvement group). The five groups were significantly different in regard to body image pursuit, self-esteem, and self-identity. The body image pursuit, self-esteem, and self-identity of adolescents were significantly different in regard to each environmental factors, in each adolescent group.