Background: The prevalence of smoking among Chinese adolescents has dramatically increased in recent years. The purpose of this study was to examine the differences in smoking-related knowledge, attitudes, and behaviors among Chinese students in 3 types of secondary schools. Methods: This cross-sectional study was conducted among 3957 students of seventh, eighth, and ninth grades and 2870 student parents from 3 public, 1 factory, and 2 general-paid private secondary schools at Guangzhou in 2004. Participants were asked to complete self-administered questionnaires about sociodemographic characteristics, smoking-related family and school environments, smoking-related knowledge and attitudes, and smoking behaviors. Results: The average scores of students' smoking-related knowledge and attitudes (higher score, more against smoking) were highest in the factory school, followed by public schools and private schools. The differences among them were statistically significantly (P less than 0.05). The lifetime smoking prevalence was also significantly different (P less than 0.001) among 3 types of schools: 35.4% in private schools, 17.4% in public schools, and 13.2% in the factory school. The prevalence of students' weekly smoking was also higher in private schools (6.2%) than in public schools (4.9%) or the factory school (4.0%). Similar disparity was observed in the prevalence of daily smoking (3.9% private, 3.5% public, and 2.7% factory). However, differences in weekly and daily smoking were not statistically significant (P less than 0.05). Conclusions: Compared with students in public and factory schools, those in general-paid private schools had poorer smoking-related knowledge, more supportive attitudes toward smoking, and more popular smoking behaviors. Therefore, more intensive smoking prevention programs should be implemented among them. (Contains 6 tables.)