Efforts toward controlling secondhand smoke in public places have been made throughout China. However, in contrast to the western world, significant challenges remain for effectively implementing smoke-free regulations. This study explores individual and regional factors which influence smoking in smoke-free public places. Participants included 16,866 urban residents, who were identified through multi-stage sampling conducted in 21 Chinese cities. The reported smoking prevalence in smoke-free public places was 41.2%. Of those who smoked in smoke-free public places, 45.9% had been advised to stop smoking. Participants stated that no-smoking warnings/signs with "please" in the statement had a better likelihood of gaining compliance and preventing smoking in public spaces. Multilevel logistic regression analysis showed that ethnicity, education, occupation, type of smoking, age of smoking initiation, smoking situation, stress, household smoking restrictions and city population were all associated with smoking in smoke-free public places. Interestingly local smoke-free regulations were not associated with smoking in public places. The findings underscore that efforts to restrict smoking in public places in China should emphasize strong enforcement, while simultaneously raising public awareness of the perils of second hand smoke.