Smoking is a worldwide problem that threatens people's health. The average age of smokers has decreased with each passing day. Thus, studies focusing on preventing children or teenagers from starting smoking or studies aiming to help people quit smoking are one of the most effective ways of the fight against smoking. In order to prevent smoking behavior of young people it is necessary to thoroughly examine the reasons of such behavior. In this study, smoking behavior of high school students was examined in the framework of Planned Behavior Theory, which is a sociopsychological theory (TPB, Ajzen, 1985). With the structural equation model, which was constructed by taking TPB components into account, factors affecting students' smoking behavior were determined. Theory of Planned Behavior has explained the smoking behaviors of the participants in 72%. It was seen that the most important TPB component that affects students' behavior is attitude, which is followed by subjective norm and perceived behavior control, respectively. The results indicate that one should work on attitude first and foremost, and thus on behavioral beliefs in order to make changes in the students' tendency to smoke, in other words, in their behavior.