Cushing's syndromes caused by ectopic corticotropin secretion represent 10 to 15% in the causes of Cushing's syndrome. Somatostatin receptor scientigraphy can be successful in the localization of ACTH-secreting neuroendocrine tumors. We report a case of Cushing's syndrome caused by ectopic corticotropin secretion from a thymic carcinoid tumor. Conventional localization techniques failed but the tumor was detected by a double binding thoracic scintigraphy using 111Indium-octreotide and 99mTechnetium-albumine macroagregates.