Objective To determine the characteristics of paresteal lipomas with hypemstosis (esteochondromas or osseous protuberances)on CT images and to improve the knowledge of diagnosis and differential diagnosis of the disease.Methods CT images and clinical history of 6 patients with pathologically confirmed parosteal lipemas with hyperostosis were retrospectively reviewed.All of the 6 patients underwent plain CT scans.Results CT images clearly show lipomas and osseous projections or osteochondroma in the 6 cases.Parosteal lipomas were found with osteochondronms in 2 cages(1 at the isehium.and the other 1 at the femoral trochanter)and willl osseous protuberances in 4 cases(2 at the diaphysis offemurs.1 at the diaphysis oftibia and the other 1 at the sternum).These osteochondromas and ossous protuberances were surrounded by the adipose component of the neoplasm and had a firm attachment oftlle neoplasm to the underlying bone.The size ofthe osseous projections varied from 0.3 cm x1.2 cm to 6.0 cm x 4.0 cm.The shape of the osgeous projections was various.Osteochondromas found in 2 cases showed cortical continuity with the adjacent bone together with marrow continuity with tlle adjacent bone marrow.In the 4 cages of parosteal lipama with osseous protuberances,2 to 4 osseous protuberances were found in 2 case8 and solitary osseous protuberance were found in the other 2 cases.The lipomatoas companent showed typical features of adipose tissue on all images.The size of the lipomas varied from 3.0 cm ×2.0 cm to 11.0 cm×10.0 cm with clear border.Fibrous septa of different thickness were found within the adipose tissue.There was essification and (or) calcification in 1 case and muscle atrophy in 2 espies.Conclusions CT scan is useful in the presurgical evaluation of parosteal lipomas witll osteochondromas or osseous protuberances became it can demonstrates the morphology,location and extent of the lesions.and it can show their relationship to the surrounding structures. It is important for differential diagnosis and preoperative assessment of the lesion.