This study compared young adults (ages 18 to 26) with and without childhood attention deficit hyperactivity disorder (ADHD) on self-reported risky sexual behaviors. Participants were 175 men with childhood ADHD and 111 demographically similar men without ADHD in the Pittsburgh ADHD Longitudinal Study (PALS). Childhood ADHD predicted earlier initiation of sexual activity and intercourse, more sexual partners, more casual sex, and more partner pregnancies. Although childhood conduct problems did contribute significantly to risky sexual behaviors among participants with ADHD, there was also an independent contribution of ADHD, suggesting that the characteristic deficits of the disorder or other associated features may be useful childhood markers of later vulnerability.