Previous research has shown that a trait termed neurobehavior disinhibition (ND) measured in childhood predicts substance use disorder by young adulthood. The present investigation extends these findings by determining the degree to which peer environment mediates the association between ND and development of cannabis use disorder (CUD). ND was measured in a sample of 216 boys 10-12 years of age. The peer environment was assessed at age 16. Current CUD was determined at age 22. Paternal and maternal SUD predicted son's ND which, in turn, predicted son's peer environment and, subsequently, son's cannabis use frequency and CUD. Peer environment mediated the association between ND and cannabis use and ND and CUD. Maternal and paternal SUD predicted the peer environment. Parental SUD, son's ND, and son's peer environment predicted CUD at age 22 with 84% accuracy.