Early onset of conduct disorder (CD) with callous-unemotional traits has been linked to low levels of dopamine β-hydroxylase (DβH), an enzyme involved in dopamine turnover. The C1021T polymorphism in the DβH gene is a major quantitative-trait locus, regulating the level of DβH. In this study of juvenile delinquents from Northern Russia (n = 180), the polymorphism at -1021 was associated neither with early-onset CD nor with psychopathic traits. Association was found between psychopathic traits and early-onset CD, ADHD and mania.