Cannabis use disorder is both common and costly. The impact of standard services for treating cannabis use and related problems has been inhibited by supply, accessibility, and perceived stigma. Thus, private, readily accessible methods of delivering evidencebased treatment on a large scale and at low cost are urgently needed. Accordingly, we developed the first mHealth smartphone app for managing cannabis use (Assess, Plan, Track, Tips; APTT). This study examines 10 cannabis users’ (50% men, aged 17-38) reactions to APTT after participating in a 2-hour in-house testing session. Eligibility criteria required participants to be interested in evaluating, reducing, or ceasing their cannabis use. Participants were satisfied with APTT overall, but rated its ease of use slightly higher than its helpfulness.