 Based on prior literature and pilot data collected during the previous Merit Review period, the primary hypotheses for the proposed research are that: 1 Participants who are heavy MJ users will have higher 4 2 nAChR densities in the thalami and other brain regions than participants who are not heavy MJ users, 2 Participants who are daily heavy caffeine users will have lower 4 2 nAChR densities in the thalami and other regions than participants who are not heavy daily caffeine users, 3 Densities of 4 2 nAChRs in the thalami and other brain regions of interest will be higher in menthol than non-menthol cigarette smokers, and 4 lesser severity of 4 2 nAChR up-regulation at baseline along with clinical factors such as lesser severity of nicotine dependence will be associated with better treatment outcomes in a standard smoking cessation program, including an improved likelihood of quitting andor decreasing smoking. 