There is a certain coincidence of getting lung cancer after quitting smoking. It is not that quitting smoking is easy to cause lung cancer; there is no clinical statement that it is easy to get lung cancer after quitting smoking. If a patient still gets lung cancer after quitting smoking, it may be due to a combination of long-term smoking, environmental or genetic factors. Long-term smokers have a higher risk of lung cancer compared with normal people, and their body tissues and immunity have been affected by harmful substances in tobacco, and quitting smoking can avoid the aggravation of this effect to a certain extent, but it usually cannot be reversed. However, no studies have shown that quitting smoking increases the probability of getting lung cancer. The occurrence of lung cancer is positively related to the amount of smoking and the age of smoking. Although quitting smoking can reduce the risk of lung cancer, the damage to the respiratory and cardiovascular systems caused by a history of smoking cannot be eliminated immediately. And the degree of damage and the time required for clearance are directly proportional to the amount and duration of smoking. Also, as the patient’s fitness declines with age, the removal of toxins will be even slower. Therefore, it is recommended to quit smoking as early as possible to reduce the damage to the body, and also to help reduce and eliminate the harmful tobacco substances that may be present in the body. Patients can have regular medical checkups after quitting smoking, and if lung abnormalities are detected early, they can be treated in time to avoid lung cancer.