BackgroundNumerous studies have shown that attention deficit/hyperactivity disorder (ADHD) is associated higher risk of cannabis use disorders (CUD). However, these studies are limited in that most did not: (a) differentiate the role of hyperactivity–impulsivity (HI) and inattention (IN); (b) control for associated psychopathology; and (c) consider more fine-grained CUD-related measures. Our aim was to clarify the unique and interactive contributions of inattention and hyperactivity symptoms to age of cannabis initiation and DSM-IV cannabis dependence, craving, and severity of problems related to cannabis use while statistically controlling for symptoms of comorbid psychopathology in a non-clinical sample of young adults. MethodsCannabis variables, current use of cigarettes and alcohol, current and childhood ADHD, and comorbid internalizing and externalizing psychopathology were assessed in 376 male and female undergraduates. ResultsResults indicate that current and childhood IN were independently associated with more severe cannabis use, craving, and problem use-related outcomes in young adulthood (p's<.01) and that childhood HI symptoms were associated with earlier initiation of cannabis (p<.01). Further, current IN symptoms moderated the relationships between level of use and more severe outcomes (p's<.01), such that higher IN strengthened positive associations among use and problem cannabis use. Associations with ADHD symptom dimensions and current use of alcohol and cigarettes were also present. ConclusionsThus, current and childhood inattention symptoms as well as childhood hyperactive–impulsive symptoms emerged as significant factors in cannabis-related outcomes in young adults, even after statistically controlling for important confounding variables.