Purpose: Because it is important to prevent adolescents from becoming involved in smoking, this study was done to explore important factors influencing cigarette use and the increase in smoking frequency. Method: For this study the Korea Youth Panel Survey (KYPS) was analyzed. Because the KYPS is longitudinal, a fixed effect regression method was used to control for the effects of time-independent factors. More specifically, a logistic regression was used to explore factors affecting cigarette use, and a Poisson regression was used to explore smoking frequency. Result: As the adolescents got older, the number of male adolescents who tried smoking increased, while the number of female adolescents who tried smoking decreased. Also, the frequency of cigarette use among male and female smokers increased over time. Significant factors affecting cigarette use were friends who smoked, delinquent behavior, and loneliness at schools. Important factors affecting the increase in smoking frequency were grade (e.g., the 2nd- and 3rd-year of middle school), friends who smoked, delinquent behavior, monthly pocket money, expectation for the highest level of education, and attack tendency. Conclusions: To solve the problems linked to adolescent smoking, it is critical to develop intervention programs that target specific homogeneous subgroups of smokers, and that take into consideration gender difference in smoking and factors affecting levels of smoking behavior.