Approximately 50% of persons seeking treatment for cannabis-use disorders (CUDs) regularly smoke tobacco. Combining tobacco with cannabis has become a common method of smoking cannabis either via use of blunts (rolling cannabis into hollowed out cigars), adding tobacco to joints, or smoking tobacco immediately after cannabis (chasing). Tobacco smoking is a negative predictor of cannabis outcomes for those trying to quit using cannabis, and vice versa. The similar route of administration and repeated pairing of tobacco and cannabis use likely results in learned associations that strengthen the behavior for using both substances, and make quitting more difficult. Perhaps even more than with use of alcohol or other drugs, stopping tobacco at the same time as cannabis may be beneficial. Little scientific information currently addresses how to best target tobacco smoking during treatment for CUDs. The long-term goal of this project is to develop an effective protocol for intervening in tobacco smoking in this population without adversely affecting cannabis outcomes, and perhaps enhancing them. A two-phase, Stage 1 therapy development project will accomplish the following three Specific Aims. First, a treatment protocol and manual will be developed that integrates a tailored intervention for tobacco smoking (nicotine replacement therapy and behavioral counseling) with an optimal intervention for CUD (Aim 1). Utilization of web-based counseling programs will standardize delivery of the intervention and foster eventual dissemination. A pilot study will provide an initial test of acceptability and feasibility, and inform modifications to the intervention. Second, a Stage 1, proof-of-concept study will compare this combined intervention to one that targets CUD only (Aim 2). The primary hypotheses assert that the intervention (1) will be accepted by the majority of CUD outpatients who smoke tobacco; (2) will result in more tobacco quit attempts and higher tobacco cessation rates than the CUD-only treatment; and (3) will not adversely affect cannabis outcomes, and possibly enhance them. Estimates of outcomes and condition differences will inform the planning and design of a subsequent Stage 2 efficacy trial. Last, the project will evaluate the potential of specific moderators of outcomes, such as impulsivity (delay discounting rate), to predict outcomes and inform subsequent treatment development efforts (Aim 3). If the hypotheses were confirmed, dissemination of this protocol would reduce adverse psychosocial and health consequences associated with tobacco and cannabis dependence. Moreover, findings will inform future development of prevention and intervention strategies by advancing knowledge related to the interplay of cannabis and tobacco smoking and the biologic and behavioral factors that contribute to initiation of use, misuse, and attempts to quit using them.