Introduction: Adolescent smoking can lead to various health problems including atherosclerosis and cardiovascular disease, making it more difficult to quit smoking during adulthood. This study aims to evaluate the effect of the ordinance by assessing adolescents' smoking cessation behaviors and environmental conditions, according to the "Ordinance for the Prevention of Child and Adolescent Smoking and Support for Smoking Cessation", which was enacted in 2019 in Gwangju City, South Korea, for the first time in the country. Methods: The data for the analysis were obtained from the 2018 and 2021 Korea Youth Risk Behavior Survey. Propensity score matching (PSM) ensured homogeneity between ordinance-adopted and non-adopted areas, followed by a difference-in-differences (DID) analysis to assess changes in adolescent smoking behavior, secondhand smoke exposure, and related advertisements. Results: The difference-in-differences analysis of the homogeneous treatment and control groups in 2018 and 2021 showed statistically significant reductions in the variables "experience of secondhand smoke indoors at school" in the secondhand smoke category, and "exposure to smoking advertisements in convenience stores" in the smoking advertising category. However, there were no statistically significant changes in the other eight variables, such as smoking behavior and smoking cessation advertising. Conclusions: The results of this study suggest that the ordinance enacted in Gwangju Metropolitan City in 2019 created a positive environment for smoking prevention in convenience stores and schools for adolescents. Furthermore, if the ordinance is supplemented with the management of smoking behaviors and smoking cessation advertisements, it is expected to achieve the main purpose of the policy, which is to protect adolescents from smoking.
Keywords: adolescent smoking; difference in differences; propensity score matching; secondhand smoke; smoking advertising.