Researchers at the University of Washington are conducting a confidential study seeking adult marijuana and tobacco users who are interested in trying to quit marijuana. The study offers a 12-24 week program that includes a combination of individual and computer assisted counseling sessions. Incentives are provided for achieving abstinence from marijuana, based on twice weekly drug testing. Participants can earn up to $435 over the course of treatment for being abstinent from marijuana. The program does not involve any groups. Each session is centered on identifying, learning, and practicing the skills needed to quit smoking marijuana. The program will also provide assistance with quitting tobacco for those who are interested, including free Nicotine Replacement Therapy (gum, lozenges, and patches). All services are provided free. Participants must be available to come to the study location in Seattle’s University District two times per week for twelve to twenty-four weeks and to participate in research assessments (also compensated).