If a patient has pain under the ribs on the right side when breathing deeply, it may be due to several reasons: 1. It may be caused by an injury to the ribs here. For example, if a patient suffers a direct violent blow to the thorax here, it may cause a contusion or even a fracture of the ribs here. This may be caused by deep breathing or coughing, which may pull on the injured area and induce very obvious pain. 2. It may be caused by gallbladder-related lesions. For example, patients with cholecystitis or cholangitis may experience similar symptoms. 3, it may also be caused by adhesive pleurisy. For example, if a patient has severe lung inflammation or other lung lesions, the inflammatory exudation in the pleural cavity may lead to such disease, which may cause pain when the pleura is pulled during deep breathing.