From the American Academy of Pediatrics: Technical report--Tobacco as a substance of abuse.

Tobacco use is the leading preventable cause of morbidity and death in the United States. Because 80% to 90% of adult smokers began during adolescence, and two thirds became regular, daily smokers before they reached 19 years of age, tobacco use may be viewed as a pediatric disease. Every year in the United States, approximately 1.4 million children younger than 18 years start smoking, and many of them will die prematurely from a smoking-related disease. Moreover, there is recent evidence that adolescents report symptoms of tobacco dependence early in the smoking process, even before becoming daily smokers. The prevalence of tobacco use is higher among teenagers and young adults than among older adult populations. The critical role of pediatricians in helping to reduce tobacco use and addiction and secondhand tobacco-smoke exposure in the pediatric population includes education and prevention, screening and detection, and treatment and referral.