This cross-sectional study examined cigarette smoking knowledge, attitudes, and practices among medical students in a southwestern region of China. The subjects included 557 and 223 first and fourth year Chinese medical students, respectively. Comparison data were collected from 74 Japanese and 90 Vietnamese fourth year medical students. The smoking rate among the fourth year medical students in China (7.0%) was significantly higher than among the first year medical students (2.8%), and higher than among the medical students from Vietnam, but lower than the medical students from Japan. The fourth year Chinese students had a more permissive attitude toward cigarette smoking by physicians compared with the first year students, and the lowest knowledge base on cigarette smoking-related diseases among the students from all three countries. Based on a multivariate analysis, the factors associated with cigarette smoking were male gender, having friends who smoked, and exhibiting a permissive attitude toward smoking. Implementations aimed at improving tobacco education and addressing the gender differences and peer influences related to cigarette smoking are needed to improve Chinese medical students’ knowledge and attitudes about cigarette smoking, and to prevent students from starting to smoke cigarettes.