Hwang JH, et al. - Using age-period-cohort (APC) analysis, researchers focused on the gender differential secular trend in adolescents’ lifetime smoking prevalence, and determined likely reasons for this trend, including Korean tobacco control policies during the last 10 years. They used the 2006–2017 Korea Youth Risk Behavior Web-based Survey enrolling grades 7 to 12. They divided students (n = 859,814) who had ever smoked into 6 age groups, 12 periods, and 17 school admission cohorts. They determined the influences of age, period, and school admission cohort on lifetime smoking prevalence by gender, employing APC analysis with the intrinsic estimator method. Between genders, lifetime smoking prevalence tended to be similarly influenced by all the three effects: an advancing age effect with grade, negative period effect with survey period, and similar pattern of school admission cohort groups. However, girls vs boys exhibited a decrease in the increasing age effect in the 12th grade, consistent and steeper declining trend in the period effect from 2006 to 2016, and shorter and lower school admission cohort effect. In this study, gender differential response to chronological alterations in lifetime smoking prevalence was measured by the APC effect, which influenced the gender differential secular trend in lifetime smoking prevalence. Thus, taking the APC effect into account could assist in understanding the trend in smoking rates, and also the contextual factors that influence it.