Background. The majority of ectopic adrenocorticotropic hormone (ACTH)-secreting tumors are localized in the chest or abdomen. Occasionally, these tumors are found in the paranasal sinuses. Methods. We present 2 unusual cases of ectopic ACTH syndrome whose ACTH-secreting tumors were localized in the paranasal sinuses and describe their biochemical and radiological presentation. Results. The first patient had an ACTH-secreting olphactory neuroblastoma originating in the ethmoid sinuses. The second patient had a clinical course and biochemical findings indistinguishable from pituitary ACTH-dependent Cushing's syndrome, except for negative petrosal sinus sampling. Head imaging showed a “polyp” in the left maxillary sinus-secreting ACTH. Both patients went into remission following surgicalresection and recovered normal pituitary-adrenal axis function. Conclusion. Ectopic ACTH secretion may originate from lesions in the paranasal sinuses. This accessible location allows for direct immunohistochemical diagnosis with ACTH staining. Surgical resection/radiation therapy can result in complete remission of the disease and restoration of normal pituitary-adrenal function. © 2008 Wiley Periodicals, Inc. Head Neck, 2009.