Objective: This study examined whether exposure to maternal smoking during pregnancy in children with and without ADHD is associated with smoking in offspring and whether this association is selective to ADHD children. Method: Ninety-six exposed and 400 unexposed participants were derived from two longitudinal studies of boys and girls with and without ADHD. Maternal smoking during pregnancy was defined by interviews with participants’ mothers. Results: A significant association was observed between exposure to maternal smoking in pregnancy and cigarette smoking in offspring (p = .02). Exposed offspring were also more likely to have higher rates of major depression (p = .04), bipolar disorder (p = .04), and conduct disorder (p = .04), and lower IQ (p = .01), lower Global Assessment of Functioning (GAF) score (p = .02), and more impaired Social Adjustment Inventory for Children and Adolescents (SAICA) scores versus unexposed offspring, adjusting for social class. Conclusion: Maternal smoking during pregnancy was found to increase the risk for smoking and a wide range of adverse psychiatric, cognitive, and functional outcomes in youth.