Mediastinal lipomatosis is a benign condition characterized by a large amount of mature adipose tissue within the mediastinum. It widens the mediastinum and may simulate mass lesions, thus leading to diagnostic errors. We describe a new case of a huge mediastinal lipomatosis and review 36 cases previously reported in the literature. Computed tomography has an important role in the diagnosis of this disease. To avoid invasive and unnecessary procedures, this diagnosis should be considered in any patient with Cushing's syndrome.