Therefore, the investigators designed a randomized controlled study to test the efficacy and safety of a smoking cessation programme with varenicline tartrate 1 mg BID in diabetic subjects who smoke. The investigators hypothesized that smoking cessation with varenicline could be associated with similar smoking abstinence rates compared to the results obtained in the general population. Given that a better understanding of predictors of smoking cessation (e.g. gender, age at smoking initiation, previous quit attempts, Fagerstrom Test Nicotine Dependence (FTND), motivation, depression, anxiety, social/familial environment, etc.) can be useful in identifying potential quitters and likely relapsers (22) and that little is known about these predictors in diabetics, the role of different predictors of abstinence at the end of the study will also be examined.