INTRODUCTIONWe describe the vaping and smoking habits of French adolescents aged 15–16 years in the Loire department with a view to assess the impact of e-cigarette experimentation and use on their smoking behavior.METHODSThis quantitative, cross-sectional, single-center and observational study conducted from January to July 2019 targeted 6622 students aged 15–16 years attending public high school in the Loire department, France.RESULTSA total of 4937 (74.6%) adolescents were included. Of these, 73.2% were non-vapers and 72.2% non-smokers; 66.0% of adolescents were non-vapers and non-smokers. Slightly less than half of adolescents had experimented with e-cigarettes (44.6%), more than half of whom (26.8%) continued to use vaping products, with 6.02% vaping daily. Likewise, a little less than half of adolescents had experimented with smoked tobacco (42.4%), more than half of whom (27.8%) continued to use smoking products, with 10.3% smoking daily. Vapers and smokers (20.6%) tended to begin with the use of smoked tobacco and to progress to the dual use of vaping and smoked tobacco products. Vaping had a positive effect, as 71.8% of vapers who smoked tobacco before initiating vaping stopped or reduced smoking following their progression to this double use. More than half of tobacco users are daily users while this daily use affects only 1/3 boys and 1/6 girls for vape. Finally, nearly 80.7% of adolescents who had never smoked before vaping did not smoke at the time of the study.CONCLUSIONSOur data suggest that vaping has a rather marginal impact on smoking initiation among French adolescents aged 15–16 years in the Loire department. They therefore neither confirm nor completely disprove the gateway effect theory, relating to use of tobacco subsequent to vaping.