Fat containing masses, except mediastinal lipomatosis, of the thorax are uncommon. In spite of uncommon occurences, as CT can detect not only the fat content but also the presence and character of the non-fatty component of the mass, accurate preoperative diagnosis can usually be made in most cases of fat containing mediastinal masses. Authors report 6 cases of fat contatining mediastinal masses, that were diagnosed preoperatively by CT scan, comprising 2 cases of limpoma(combined with plexiform neurofibroma in a case), 1 liposarcoma, 1 thymolipoma, and 2 cases of omental hernia through Morgagni foramen.