According to the National Survey on Drug Use and Health (NSDUH), the most commonly abused substance among teens is alcohol, followed by tobacco. The most commonly abused illegal drug is marijuana. In 2006, 16.6% of 12 to 17 year olds had abused alcohol, 10.4% had abused cigarettes, and 6.8% had abused marijuana in the month prior to the survey.

You can learn more about drug abuse trends and statistics at: http://www.drugabuse.gov/related-topics/trends-statistics