ObjectivesTo understand a 20-year trend of gender-specific smoking prevalence among adults in South Korea.DesignAge-period-cohort analysis using the intrinsic estimator method was applied to examine the separate contribution of age, period and cohort effect on smoking prevalence. The Driving Force-Pressure-State-Exposure-Effect-Action (DPSEEA) framework was used to explain the observed smoking trends by mapping potential determinants and to address policy implications.SettingGeneral adult population in South Korea.Participants34 828 men and 43 632 women who aged 19–78 years, were not currently pregnant and were without a prior diagnosis of cardiovascular disease or cancer.Outcome measuresGender-specific current smoking prevalence using the 1998–2017 Korea National Health and Nutrition Examination Survey.ResultsOur results showed gender-specific age and birth cohort effects. More specifically, the smoking prevalence peaked at their mid-20s (prevalence rate ratio (PRR): 1.54, 95% CI: 1.49 to 1.59) and cohort born in 1959–1963 (PRR: 1.63, 95% CI: 1.57 to 1.70) and then decreased in men. On the other hand, in women, the smoking prevalence consistently increased until their mid-40s (PRR: 1.53, 95% CI: 1.27 to 1.84) and in recent birth cohort groups (PRR in 1994–1998 cohort: 1.55, 95% CI: 1.13 to 2.13). The period effects declined from 1998−2002 to 2003–2007, following increasing fluctuations in both genders. The smoking-DPSEEA framework showed the absence of policy actions to target female smokers and emphasised a proactive approach that tackles the upstream causes for smoking in women.ConclusionsMen and women are clearly in different phases of the smoking epidemic in Korean population, and gender-tailored policies should be implemented.