Pneumonia and lung cancer are two diseases of completely different nature. Recurrent pneumonia is a risk factor for lung cancer, but it does not mean lung cancer. Pneumonia usually manifests as fever, cough and sputum, and is caused by bacterial, viral and mycoplasma infections. Lung cancer is a malignant tumor originating from the bronchial mucosa or glands in the lungs, accompanied by symptoms such as cough, hemoptysis and chest pain. Pneumonia and lung cancer are two completely different diseases. Pneumonia is milder and has a better prognosis, while lung cancer has a poor prognosis and a high mortality rate. However, long-term chronic inflammation stimulation is a factor that induces cancer. When a certain part of the lungs is repeatedly infected, this part is stimulated all the time. And the constant irritation of the same area increases the risk of cancer in that area, but the probability of this tends to be low. Therefore, recurrent pneumonia should be taken seriously, the cause should be identified and treated thoroughly to avoid recurrence. In addition, for middle-aged and old-aged patients who have been smoking for a long time, when they have repeated localized lung infections, they need to be alert to the occurrence of cancer, and in addition to the diagnosis of pneumonia, they should also undergo chest CT and fiberoptic bronchoscopy and other tests in a timely manner to make a clear diagnosis, so as to avoid delaying the condition and missing the best time for treatment.