The purpose of this research was to study smoking behavior and prediction of influence factors for smoking behavior of private vocational students in Thonburi Side Bangkok. It was mixed methodology design. There were 2 steps: 1) Qualitative research: the key informants were selected by purposive sampling. The key informants were 20 persons together with teachers 5persons, students who smoke 10 persons and friends of students who smoke 5 persons. Analyze data was the triangulation method. 2) Quantitative research: The samples were students who smoke 425 persons which were randomly selected by multistage random sampling. Analyze data were mean, standard deviation, coefficients, and stepwise multiple regression analysis. The results of the research found that 1) the smoking behavior of most students smoked less than 10 cigarettes per week. 2) Factors influencing the smoking behavior of students: 2.1) school (X1) 2.2) access to the source of purchasing cigarettes (X2), 2.3) family influence (X3) 2.4) cigarette graphic warning labels (X4) 2.5) support from friends who smoke (X5) 2.6) smoking attitudes (X6) and 2.7 Measures to prevent smoking in public places (X7).