There are many reasons for the vague pain behind the sternum, such as respiratory diseases, heart diseases, pleural diseases, digestive diseases, bone diseases and so on. 1. Respiratory diseases: Pneumonia, bronchitis, lung cancer and other diseases can show the phenomenon of vague pain behind the sternum, accompanied by coughing, coughing up phlegm and other phenomena. 2. Heart diseases: myocardial infarction, angina pectoris, myocarditis and other diseases can also show hidden pain behind the sternum, accompanied by arm pain, dyspnea, palpitation, chest tightness and other symptoms. 3. Pleural diseases: pleurisy can also cause vague pain behind the sternum, accompanied by dyspnea and sternal pain. 4. Digestive diseases: reflux esophagitis, gastric ulcer, gastritis, duodenal ulcer and other diseases can also lead to vague pain behind the sternum, accompanied by black stools, abdominal distension, nausea, belching and other symptoms. 5. Skeletal diseases: sternal fracture, sternitis and other diseases can also cause vague pain behind the sternum. Causes of hidden pain behind the sternum is very many reasons, after the symptoms need to consult a doctor in a timely manner, after a clear diagnosis, follow the doctor’s instructions to take standardized treatment, should not be ignored, so as not to delay the condition.