This study examines the feasibility of recruiting and retaining adolescents and young adults with frequent cannabis use for a 2-week momentary sampling study of cannabis use. Participants responded to random signals on a handheld computer with reports of their use. Participants also initiated reports pre- and post-cannabis use. Participants had high rates of completion (93%) and response to signals (74%) and low study burden. Cannabis use influenced the validity of the data (p < 0.05). These findings highlight the feasibility of recruiting and retaining adolescent/young adult cannabis users in a momentary sampling study. Data validity may be affected by substance use.