The Prevalence of cannabis use disorder (CUD) has been steadily increasing within the Veteran Health Administration (VHA), along with the related significant physical, cognitive, and psychological sequelae. Even in patients with a strong motivation to quit and the presence of empirically-supported interventions (Roffman & Stephens, 2006), Veterans who receive treatment for CUD have high rates of lapse (63% by 6-months post- treatment) and relapse (71% within 6-months post-treatment; Moore et al., 2003). Thus, identifying strategies to improve response to CUD treatment is in the interest of all VHA stakeholders. Disturbed sleep is common among individuals with CUD and has been shown to result in increased rates of lapse/relapse to cannabis (Babson et al., 2012). In fact, 48%-77% of individuals making a cannabis cessation attempt report lapsing/relapsing specifically to manage poor sleep (Copersino et al., 2000; Levin et al., 2010). Therefore, when individuals with poor sleep attempt to quit using cannabis, not only is their coping mechanism removed, but they are also likely to experience withdrawal-related sleep difficulties, increasing risk for lapse/relapse. Providing a behavioral sleep intervention within the context of CUD treatment, and prior to a cessation attempt, has the potential to improve these cessation outcomes. Cognitive behavioral therapy for insomnia (CBT-I) is a well-established first-line treatment for insomnia. While CBT-I is being disseminated throughout VHA, it is rarely received by Veterans with substance use disorders (SUDs) and, among those that do receive it, it is almost always delivered following a cessation attempt. While CBT-I has been shown to be an effective treatment for improving sleep among individuals with insomnia and co-occurring conditions, including SUDs, there has yet to be an investigation of the impact of providing CBT-I prior to CUD treatment with the goal of improving cessation outcomes. In addition, the development of an adjunct behavioral intervention delivered via mobile app technology within VA holds great promise to bolster CBT-I outcomes, however, such an approach has yet to be evaluated. The proposed CSR&D CDA-2 seeks to fill this gap by conducting a randomized prospective study designed to evaluate the efficacy of CBT-I, as well as the incremental benefit of including an adjunctive sleep mobile app (CBT-I-MA), on both cannabis cessation and sleep outcomes among Veterans with CUD. We will test the following specific aims: Aim 1: Veterans receiving CBT-I-MA or CBT-I (compared to a placebo): (1.1) will experience greater reductions in cannabis use frequency over the 2-weeks, 4-weeks, and 6-months post- cessation; (1.2) and have greater point prevalence abstinence (PPA) over time. Aim 2: Those receiving CBT-I- MA or CBT-I (versus placebo) will experience (2.1) improved sleep quality; with (2.2) group-based differences in cannabis outcomes over time explained by sleep quality over time. In addition, those who receive CBT-I-MA will evidence better cannabis cessation and sleep outcomes compared to those who receive CBT-I alone. Exploratory analyses will evaluate mechanisms accounting for this difference. To test these aims, 168 Veterans with CUD and insomnia will be randomized into one of three groups: (1) CBT-I with adjunctive sleep mobile app (CBT-I-MA); (2) CBT-I only (CBT-I); or (3) Placebo-control (PC). Individuals will then complete assessments at 2-weeks, 4-weeks, and 6-months post-quit. Our primary outcomes will be evaluated over time and secondary analyses will examine effects at each time point. Findings from the proposed study will inform clinical practice and policy by investigating whether the inclusion of a behavioral sleep intervention, within the context of existing SUD treatment, will improve treatment outcomes. In addition, the incremental benefit of including an adjunctive mobile app will be evaluated, as well as mechanisms underlying this benefit. Findings will set the stage for an effectiveness study of CBT-I (supplemented by mobile app) to directly address the critical need of improving SUD outcomes.