On unenhanced CT scans, a variety of mediastinal masses contain areas with attenuation values higher than the attenuation value of the chest wall musculature. The increased attenuation may be diffuse or focal and may be a result of calcium deposition, high iodine content, or areas of acute hemorrhage. This report illustrates the gamut of high-attenuation mediastinal masses seen on unenhanced CT. Masses that are of high attenuation only on IV contrast-enhanced images (e.g., aberrant vessels) are not included.