: ADHD is a developmental risk factor for cannabis misuse and cannabis use disorder. Individuals with ADHD also struggle to cope with negative affect and are more likely to engage in potentially maladaptive, avoidant coping behaviors. Such responses may be particularly salient in college, a developmental period characterized by increased stress and autonomy and easy access to highly reinforcing substances. However, despite this increased risk, little is known about mechanisms underlying the association between ADHD and cannabis use among college students. : This two-week daily diary study examined associations between ADHD, baseline coping motives (i.e., using cannabis to avoid or reduce negative affect), and frequency of cannabis use in a sample of heavy-drinking college students (49% female) with (=42) and without (=30) ADHD. : Results showed that ADHD was significantly associated with elevated coping motives at baseline and more cannabis use days on daily diaries. Additionally, there was a significant indirect effect of ADHD on number of cannabis use days through baseline coping motives; students with ADHD endorsed a stronger drive to use cannabis to cope with negative emotions, which in turn was associated with more cannabis use days. : Findings align with theory linking ADHD to increased vulnerability for avoidant coping behaviors. Further work may explore the potential of targeted, proactive interventions to help college students with ADHD build and utilize adaptive substance-free coping skills, particularly during this challenging developmental period.