Background: Substance abuse in adolescents with diabetes mellitus (DM) is associated with the development of acute and chronic complications. Objective: To determine the prevalence of alcohol, tobacco, and illicit drug consumption in adolescents with DM and compare it with the prevalence in a large contemporary control (C) group. Methods: Adolescents with and without DM, who were attending 8th-12th grades, answered a structured written questionnaire, which evaluates the voluntary declaration of tobacco, alcohol, and illicit drug consumption. Subjects with DM were recruited from free diabetes camps or public hospitals (n = 93). The C group was obtained from a nationwide study of prevalence of substance abuse (n =58 489). For illicit drugs (marijuana, cocaine, or cocaine sulfate), results are shown as life prevalence (ever used the substance). For alcohol and tobacco, results are shown as last month prevalence (the substance was used during the last month). Results: Adolescents with DM s