CT and MR imaging allow earlier diagnosis and more specific characterization of anterior mediastinal masses than is possible with plain film radiographs. This review describes state-of-the-art CT and MR imaging of the anterior mediastinum. After a discussion of CT and MR imaging and indications for their use, normal and abnormal CT and MR findings in the anterior mediastinum are reviewed. Abnormalities include benign and malignant neoplasms, cysts, and mediastinal thyroid. Several masses such as thymolipomas, goiters, cysts, and lymphangiomas often do not require removal and now can be diagnosed with reasonable accuracy when imaging results are combined with clinical history. Detection, diagnosis, staging, and follow-up of malignant anterior mediastinal masses are important and have been improved with CT and MR imaging.