ObjectivesSmoke-free legislation was implemented in Guangzhou on 1 September 2010. However, the smoke-free policy did not cover all indoor areas and smoking rooms can be set in some public places. This study aimed to assess changes in self-reported second-hand smoke (SHS) exposure in different types of venues and in homes, in order to evaluate the effectiveness of smoke-free legislation.Methods/designA repeated cross-sectional survey of representative participants was conducted in Guangzhou before and after the smoke-free legislation. Logistic regression models were used to examine the effectiveness of smoke-free legislation.Main outcome measuresSelf-reported exposure to SHS,antitobacco advertisements and tobacco advertisements.ParticipantsA total of 4900 participants before the ban and 5135 participants after the ban were selected using a multistage stratified design.ResultsIn full smoking ban places, overall self-reported SHS exposure has declined significantly from 58.8% to 50.3% (p<0.05) with greater drops in cultural venues, government offices and commercial venues. The smoke-free policy did not alter SHS exposure in smokers’ homes (39.6% in 2009 vs 40.0% in 2011; p=0.454). Although a slight decrease in SHS exposure was observed in smoking rooms in hotels, workplaces, restaurants, cafes/bars/nightclubs and amusement parks, SHS continued to be high in those areas. The implementation of smoke-free legislation was accompanied by an increase in antitobacco advertisements.ConclusionsSHS exposure declines more significantly in full smoking ban places than in partial smoking ban places. The smoke-free policy in public places does not lead to more SHS exposure in homes. Therefore, it is recommended that Guangzhou should implement a 100% smoke-free policy in all public places and workplaces in the future.