Hidden pain in the left lung may be related to lung disease, pleural disease, heart disease and so on. 1. Lung diseases: such as left-sided pneumonia, lung cancer and other diseases, can lead to symptoms of vague pain in the left side of the lungs, patients may also be accompanied by coughing, shortness of breath and other uncomfortable symptoms. 2. Pleural diseases: left pleurisy, pleural tumor and other diseases can also cause vague pain in the left side of the lung. 3. Heart disease: angina pectoris, coronary heart disease, myocardial infarction and other heart diseases can also lead to the patient to appear in the left side of the lung vague pain and other symptoms. The cause of left-sided lung pain is relatively complex. It is important to consult a doctor as soon as possible to confirm the diagnosis of the condition, and then follow the doctor’s instructions for treatment.