The development of CT provide a noninvasive safe technique for imaging the orbit in any palne exquisitelydemonstrating its normal anatomy as well as its pathologic process. The orbit is an ideal structure to be examinedby CT because of large difference of absortion values between the intraorbital fat, muscle, optic nerve andvessels. In this study, the authors reviewed CT findings of 66 pathologically proven orbital tumors and tumorousconditions among the total of 98 cases who had taken orbital CT scan because of exophthalmos, ocular pain,diplopia and other opthalmologic symptoms suggesting orbital masses during the period of 3 years. For the anlaysisof characteristic CT findings of the orbital lesions, all lesions are divided into 4 groups according to the siteof origin, i.e., tumors arising in the eyeball(group1); from intraconal space(group 2); from extraconalspace(group3); and from extraorbital regions (group 4). The resutls are as follows: 1. Exact tumor detection andlocalization was possible in 63 cases. Thus the detection rate was 95% with CT scan. 2. Among 36 males and 30females, their age ranged from 10 months to 72 years. 3. Intraocular tumors(group 1) were 10 cases. Retinoblastomaoccurred wholly in the young children under 5 years and combined with calcification in 57%. Choroidal melanomaoccurred wholly in adutls. 4. Intraconal tumors (group 2) were 9 cases. Vascular tumors(7 cases) were the mostfrequent and well enhancing mass. 5. The tumors arising in the extraconal region(group 3) were pseudotumor(12cases), lymphoma( 3 cases), dermoid cyst(4 cases), metastasis(2 cases), adenoid cystic carcinoma(1 case) andteratoma(1 case). A case of lymphoma demonstrating retroulbar ill defined mass with scleral thickening could notbe differentiated from the poseudotumor which showing similar finding. 6. The lesions arising from extraorbitalregion(group4) were PNS cancer (9 cases), mucocele(3 cases), lid cancer (4 cases), fibrous dysplasia(3 cases) andneurofibromatosis(1 case). 7. Thin slice thickness of the transverse axial scan and reconstruction of image invarious planes provide better 3 dimensional image and are useful fo the evaluation of the characteristics of themass and its relation to other structures. 8. Contrast enhancement is useful in differentiation of vascular tumorsand other nonvascular tumors, and evaluation of the scleral thickening in pseudotumors. Evaluation of tumorextension is also possible with contrast enhancement, but in extraconal mass contrast enhancement was not helpful. 9. The CT is the method of choice in the detection and differential diagnosis of the orbital masses and evaluationof the extension of the mass.