<h4>Background</h4>Numerous 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.<h4>Methods</h4>Cannabis 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.<h4>Results</h4>Results 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.<h4>Conclusions</h4>Thus, 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.