In daily clinical work, we often see that many patients with lung cancer had a history of “pneumonia” before being diagnosed with lung cancer, and some patients may have similar history for several times before they are further examined and clearly diagnosed with lung cancer. These patients started with symptoms of fever, cough and sputum, and chest radiographs revealed “inflammatory infiltrates” in the lungs, which were reduced until they disappeared after applying “anti-inflammatory drugs”. The patient and the doctor did not further examine the cause of inflammation until the patient repeatedly showed signs of pneumonia in the same area and it took a long time for further examination, which delayed the disease and made further treatment difficult. So, what kind of pneumonia caused by lung cancer is it? Lung cancer that originates in the larger bronchus, due to the growth of the tumor, obstructs the bronchus, and the distal secretions gather and cannot be discharged effectively and become infected, resulting in inflammation of the distal lung tissue, called obstructive pneumonia. Patients with obstructive pneumonia may show symptoms of lung infection such as fever, cough and sputum, but it is different from ordinary pneumonia. First, the symptoms of obstructive pneumonia are slow to start compared with those of ordinary pneumonia, usually with a low fever of 37-38°C. The patient’s symptoms of infection and toxicity are mild; second, patients with obstructive pneumonia respond poorly to antibiotic therapy, i.e., the effect is slow after the application of “anti-inflammatory drugs” and it is difficult to make the chest X-ray “inflammation” completely dissipate. Thirdly, obstructive pneumonia is prone to recurrence, and the same area can show infection again some time after the last inflammation is controlled. Therefore, for middle-aged and elderly patients, especially long-term and heavy smokers, localized lung infections with atypical symptoms should be alerted to the possibility of lung cancer, and should not be satisfied with the diagnosis of pneumonia only, while the recurrence of infection in the same area is more suggestive of lung cancer or other causes of bronchial obstruction.