The pain in the right side of the chest when inhaling may be caused by chest injury, pneumothorax, lung infection or malignant tumor. 1. Chest injury: such as car accidents, falls, etc. can cause blunt injury to the chest, such injuries are usually not easy to find in the early stage, and pain can occur due to the expansion and contraction of the chest during inhalation. 2. Pneumothorax: Chest fracture, violent blows, etc. can make the patient’s lung tissue and chest cavity traumatized, when the chest wall rupture will lead to pneumothorax, the patient can have chest pain when inhaling, also can be accompanied by chest tightness, dyspnea and other symptoms. 3. Lung infection: if the lungs are invaded by Mycobacterium tuberculosis or bacteria, fungi and other pathogens, diffuse inflammation will also appear in the lungs, which will cause chest pain, and the pain will be aggravated when breathing deeply or coughing. 4. Malignant tumors: when malignant tumors appear in the alveolar or bronchial area, chest pain will also occur. There are other causes of inhalation chest pain, and it is recommended that patients seek medical attention in time to avoid delaying their condition.