The article describes a patient with a right paratracheal bronchogenic cyst in whom the preoperative diagnosis was unclear. The fluid component of the cyst was not readily apparent by CT or T1-weighted MR images. Very intense signal on T2-weighted MR images suggested a cystic lesion. Inhomogeneities evident on MR but not CT images provided further soft tissue characterization. These soft tissue elements correlated with a macroscopic ring of hyaline cartilage in the resected specimen. The usefulness of MRI for the differential diagnosis of mediastinal tumors is discussed.