This article presents a study comparing the self-esteem and mental health of secondary school students in three metropolitan cities in China: Hong Kong, Shanghai, and Beijing. Before 1997, Hong Kong was under the sovereignty of the British government. After the unification, the city became one of the major economic and political centers corresponding to the other two major cities. In this study, the General Health Questionnaire (GHQ-30) and the Rosenberg Self-esteem Scale (SES) were used as measuring instruments. The subjects were junior and senior secondary school students: Hong Kong (N = 1,149), Shanghai (N = 1,987), and Beijing (N = 1,922). No significant difference was found between the self-esteem of students in Beijing and Shanghai, but the self-esteem in the students of both cities was higher than in those from Hong Kong (p <.001). The mental health of Shanghai students was the best among the three cities, followed by Beijing students (p < .001) and Hong Kong students (p <.001). The factors affecting students' self-esteem and mental health in the three cities are explored and the possible explanations for the differences discussed.