Study Design The study is a double-blind, placebo-controlled, randomized, clinical trial designed to assess the efficacy and safety of varenicline 1 mg BID in comparison to placebo for smoking cessation in diabetic smokers. The duration of active treatment will be 12 weeks and participants will be followed in the nontreatment phase for an additional 12 weeks (24 week time point). This clinical study has an optional research component to prolong the follow up in the nontreatment phase for a full year (52 week time point). Predictors of abstinence at the end of the study will also be examined.