On average, adults who smoke cigarettes weigh less than nonsmokers. However, they have a greater tendency towards abdominal obesity, and, when they stop smoking, about 80% of them gain weight. Whereas original estimates of the amount of weight ex-smokers gain in one-years time was about five pounds, long-term follow-up of sustained quitters suggests that the weight gain may be considerably greater. While the health benefits of quitting smoking outweigh the adverse health consequences of post-cessation weight gain, studies on the effects of smoking cessation on lung function show that the weight gained by quitters may significantly reduce the beneficial effects of smoking cessation on lung function. Prevention of post-cessation weight gain has proved to be an elusive target. However, studies show that life style changes, diet, exercise, and pharamacotherapy, alone and in combination, may reduce post-cessation weight gain, at least for the period of time that the treatments are in effect. Nicotine replacement therapy, bupropion SR, and, to a lesser extent, varenicline, are the most effective pharmacological deterrents to post-cessation weight gain, although the latter medication may yield the best quit smoking results. Research on pharmacogenetics and other medications may increase physicians armamentarium in the future.