Our friends at the American Heart Association tell us that "Smokers have a higher risk of developing many chronic disorders, including atherosclerosis - the buildup of fatty substances in the arteries - which can lead to coronary heart disease, heart attack (myocardial infarction) and stroke. Controlling or reversing atherosclerosis is an important part of preventing future heart attack or stroke."
Their website also has an incredibly useful list of resources when and if you do decide to quit smoking - including American Cancer Society, American Lung Association, and Nicotine Anonymous.