Why do some people think that smoking is not harmful to health? As mentioned above, there are many disease-causing and carcinogenic substances in tobacco smoke, and it is certain that smoking can cause diseases. Relevant research data show that smoking is a risk factor for many diseases, and tobacco smoke can damage almost all organs of the human body. However, the health damage caused by smoking is characterized by a long-term lag. The so-called long-term lag is that most of the harm caused by smoking is not immediately manifested in the initial smoking, but more in the smoking 10 years, 20 years, or even more time, the relevant diseases will appear. It is because of this characteristic of the harms of smoking, smokers often do not recognize the harms of smoking before the disease occurs, or even if they are sick, they do not think that the disease is related to smoking, but mistakenly believe that smoking does not affect health. Because of the lack of sufficient knowledge of the health hazards caused by smoking, but smokers are not strong will to quit smoking, but also one of the reasons why it is difficult for smokers to quit smoking. Xing Guohong, Department of Respiratory Medicine, Jinan Military General Hospital, Jinan, China