Lung cancer is the number one malignant tumor in the world in terms of incidence and mortality, and this rate is increasing year by year. Current research has found that air pollution including smoking is the most important predisposing factor for lung cancer. Many people may be in the early stage of lung cancer development, but since early lung cancer is very insidious and not easily detected by patients or through ordinary X-ray, more sensitive examination means are needed to screen for early lung cancer. And early detection and early diagnosis of lung cancer becomes the most critical step, which is the only promising way to cure lung cancer at present. To detect early lung cancer, we must take the help of chest CT. When we unintentionally find a suspicious small nodule or lump in the lung by chest CT, we can immediately turn to the respiratory physician of the hospital for help. The respiratory physician will arrange further tests to clarify the nature of the lesion in the lung. Through careful screening and reading of chest CT in outpatient clinics and medical checkup centers, many patients with early stage lung cancer have been detected, holding the door to lung cancer, the most aggressive and premier malignancy in the world today. Of course, even if lung cancer patients are detected late and are already in the middle and late stages, they should not give up treatment. Through perfect whole-body assessment, individualized treatment plans are made according to each patient’s different conditions to prolong life and quality of survival. At present, lung cancer treatment has made great progress, and various chemotherapy regimens and molecular targeted therapy drugs have emerged, and lung cancer drugs often fail after a period of treatment, and then clinicians can switch to another drug, which is like a “relay race”. This has greatly improved the survival time of patients. Some people say that there is no problem if there is no lung lesion, but such a view often leaves out the problem of mediastinal lymph nodes, which are located in the gap between heart and lung and are usually less than 5mm under normal circumstances. Although many lung cancer patients do not have a large lung lesion and have not yet experienced any discomfort, the mediastinal lymph nodes have already become enlarged. In view of the above, it is recommended that people over middle age should receive a chest CT examination once a year, even if there is nothing wrong in the lungs, and patients with enlarged lymph nodes should actively seek the help of a respiratory specialist. It is strongly recommended that people with the following conditions should come to the hospital immediately for chest CT examination: 1. people with chest pain or chronic cough; 2. people with blood in sputum or whole mouth hemoptysis; 3. middle-aged people with a long history of smoking; 4. people with significant weight loss or chest tightness over the past 3 months.