The differential diagnosis of lung cancer and pneumonia is as follows: 1. Lung cancer is characterized by cough, coughing sputum, coughing blood, chest pain, and some patients also have symptoms such as cachexia and corresponding metastatic lesions, while the general condition of pneumonia is relatively good, with coughing, coughing purulent sputum, occasionally blood in sputum, accompanied by chills, fever and other discomforts, and local chest pain when pleurisy is present. 2. Patients with lung cancer can be differentiated accordingly, and patients with lung cancer can mostly see the formation of occupying lesions or obstructive pneumonia, while patients with pneumonia can mostly see two lungs or unilateral patchy inflammatory lesions, sometimes accompanied by the formation of cavities or solid shadows. The diagnosis of lung cancer also requires corresponding pathological biopsy, such as through bronchoscopy or percutaneous lung puncture.