This study used latent class regression to identify latent trajectory classes based on individuals' diagnostic course of substance use disorders (SUDs) from late adolescence to early adulthood as well as to examine whether several psychosocial risk factors predicted the trajectory class membership. The study sample consisted of 310 individuals originally recruited as children in a long-term prospective study. Diagnoses of alcohol or cannabis use disorders (abuse or dependence) were assessed when individuals were 18 (T1), 20 (T2), and 22 (T3) years old. The results showed that two trajectory classes were identified for both alcohol and cannabis use disorder cases and that the trajectory class membership was predicted by being male, dropping out of high school, receiving a diagnosis of CD or ODD in childhood, having an early age of onset of alcohol or cannabis use, previously using illicit drugs other than cannabis, and the number of risk factors an individual is exposed to. Prevention work should focus on the individuals exposed to these risk factors previously to decrease their likelihood of transition from drug use or single diagnosis to repeated diagnosis during the early years of emerging adulthood. (Contains 3 tables and 2 figures.)