Lung cancer patients may have full moon face. Clinically, the cause of full-moon face in some lung cancer patients is mainly due to excessive secretion of adrenocorticotropic hormone in patients’ body, thus making patients develop Cushing’s syndrome, in addition to the manifestation of full-moon face, patients will also have symptoms such as flushing, buffalo back, diarrhea and so on. There are three main reasons for excessive secretion of adrenocorticotropic hormone in lung cancer patients. Lung cancer has metastasized to adrenal glands, thus causing exuberant hormone secretion. Lung cancer belongs to the rare type of carcinoid tumor, which is easy to secrete excessive adrenocorticotropic hormone. Ectopic adrenocorticotropic hormone syndrome occurs in lung cancer, resulting in extrapulmonary manifestations of lung cancer such as full moon face. Patients are advised to go to the hospital as soon as possible to avoid delaying their condition.