While the demographic characteristics of women who smoke during pregnancy are well established, less is known about psychiatric characteristics that may differentiate among persistent smokers, spontaneous quitters, and nonsmokers. The purpose of the present study was to test the hypothesis that a history of externalizing problems is related to persistent smoking during pregnancy. Participants included 93 pregnant women (mean age=28 years; 89% non-Hispanic White; 46% persistent smokers; and 16% spontaneous quitters). Externalizing problems, as evidenced by conduct disorder (CD) and attention deficit hyperactivity disorder (ADHD), were assessed using diagnostic interviews. History of CD and ADHD varied by smoking status, with persistent smokers most likely to have a history of both disorders and exhibiting the highest levels of symptomatology. In multivariate analyses, a history of CD, but not ADHD symptoms, distinguished women who persisted in smoking during pregnancy from spontaneous quitters. Results suggest that a childhood history of conduct problems is a risk factor for maternal smoking during pregnancy and that psychiatric history is important to consider in developing more targeted cessation interventions.