This study examined whether a coping-skills-based treatment for marijuana dependence operated by encouraging the use of coping skills or via other mechanisms. Participants were 450 men and women treated in the multisite Marijuana Treatment Project who were randomly assigned to motivational enhancement therapy plus cognitive-behavioral (MET-CB) treatment, motivational enhancement therapy (MET), or a delayed treatment control group. Marijuana use and coping skills were measured at baseline and at follow-ups through 15 months. Results showed that marijuana outcomes were predicted by treatment type and by coping skills use, but that the coping-skills-oriented MET-CB treatment did not result in greater use of coping skills than did the MET treatment. The results suggest that mechanisms of coping skills treatment may need to be reconceptualized. Copyright 2005 by the American Psychological Association.