A series of 6 mediastinal tumors of mesenchymal origin is presented. This type of tumors is very heterogeneous in its histology, depending on the differentiation of the primary mesenchymal cell. Presenting symptoms are not diagnostic: nevertheless malignant neoplasms are often revealed by vague thoracic pain, while benign masses usually show the tendency to a slow non infiltrating growth accompanied by faint symptoms of mediastinal compression syndrome. Mesotheliomas and liposarcomas are the most frequent malignant neoplasms, while lipomas are the most represented among the benign ones. Preoperative diagnosis is often casual, based on plain X-ray examination of the chest: subsequent thoracic CAT is of utmost advantage, providing the exact definition of the limits of the mass and of its ability to invade visceral and vascular structures of the mediastinum. Lipomas are well identified by CAT because of their characteristic attenuation value. Surgical operation is mandatory, because benign neoplasms can be effectively cured and infiltrating masses correctly staged and identified by histological examination.