Objective This study, conducted in China, evaluated the effectiveness of four different themes of health warning labels (HWLs) that used both text and pictures: (1) self-harm from using cigarettes, (2) harming family or children with secondhand smoke, (3) reinforcing compliance with existing smoke-free policies and (4) anticigarette gift giving practices.

Methods A cross-sectional randomised experimental survey was conducted among 3247 adult (aged 18+ years) participants in Beijing, Shanghai and Shenzhen in 2017, using quotas for age group, gender and smoking status. Participants were randomly assigned to one of the four HWL themes. Each participant viewed eight HWLs and rated how effective these themed-labels were in terms of credibility, raising awareness of health harms of smoking on family and children, improving compliance with public smoking bans, stopping the practice of gifting cigarettes, thinking about quitting and preventing smoking using a 10-point scale, with 10 being most effective. Analysis of variance and independent t-tests were used to analyse these data.

Findings All four HWL themes performed well for each outcome with average ratings >6.5. Harming family or children with secondhand smoke was the theme that received the highest ratings for each outcome, with credibility (8.0, 95% CI 7.86 to 8.09) and prevention of smoking (8.8, 95% CI 8.63 to 8.91) outcomes being significantly higher (p<0.05). Overall, analysis of ratings by gender, income and education did not impact outcomes.

Conclusion All four HWL themes tested could be effective in China; the theme of secondhand smoke harming family or children may be a particularly credible/effective theme.