A large number of epidemiological studies worldwide have confirmed that smoking is a risk factor for many diseases. The main diseases caused by smoking are: 1. Lung cancer and many malignant tumors: more than 90% of lung cancers are caused by smoking, and the incidence of lung cancer in smokers is 18 times higher than in nonsmokers. Smoking can also cause oral cancer, laryngeal cancer, esophageal cancer, stomach cancer, pancreatic cancer, bladder cancer, kidney cancer, liver cancer, leukemia, as well as female cervical cancer, breast cancer, etc. Jinan Military General Hospital, Department of Respiratory Medicine Xing Guohong 2, chronic obstructive pulmonary disease: smoke tar and other harmful substances in the long-term stimulation of the respiratory tract, making smokers very vulnerable to chronic bronchitis, asthma, emphysema, and finally lead to chronic obstructive pulmonary disease, pulmonary heart disease. The rate of chronic obstructive pulmonary disease among smokers is three to five times higher than that of nonsmokers. The more you smoke, the longer you smoke, the earlier you start smoking, the greater the risk of COPD. 3, cardiovascular disease: tobacco tar, carbon monoxide and other toxic substances, can damage the heart muscle and blood vessel walls, causing disorders of cholesterol metabolism, high-density lipoprotein deficiency, resulting in hypertension, hypercholesterolemia, atherosclerosis and other disorders; smoking increases blood viscosity, prompting blood 4, cerebrovascular disease: smoking can increase the risk of cerebral hemorrhage, cerebral infarction and subarachnoid hemorrhage. The risk of stroke among smokers in China is 2 to 3.5 times that of nonsmokers, and more than 90% of male stroke patients are smokers. 5, digestive system diseases: smoking can cause peptic ulcers, gastritis and esophageal and colonic disorders, especially peptic ulcer relapse. 6, endocrine diseases: smoking 20 cigarettes a day can increase the risk of diabetes by a factor of 1. Smoking also promotes thyroid disease.7, oral diseases: the lighter the oral odor, yellow teeth, the heavier can cause lip cancer, oral cancer, oral leukoplakia, Candida albicans infection.8, ophthalmic diseases: can cause toxic optic neuropathy, visual hypoadaptation, macular degeneration, cataracts.9, smoking can also cause blood disease, osteoporosis and other diseases and male sexual dysfunction.