In the diagnosis of chest diseases, MR imaging has been shown to be most helpful in the evaluation of hilar and mediastinal lesions. The detection of intrathoracic abnormalities is technique-dependent, and imaging with both short and long repetition and echo times is necessary. ECG gating and sagittal or coronal images supplement transaxial scans in some patients. MR allows the diagnosis of mediastinal vascular lesions and the differentiation of mediastinal mass and vessel without contrast agents. It provides diagnostic information quite similar to that of CT in patients with mediastinal mass, but spatial resolution is somewhat poorer. In patients with hilar mass, MR is superior to CT in identifying the mass and distinguishing it from normal structures.