PURPOSE: To evaluate CISS MR imaging findings of epidermoid tumor in comparison with conventional spin-echoimages. MATERIALS AND METHODS: We studied 6 cases of epidermoid tumor in the subarachnoid space. We used a 1.5TMR unit to obtain CISS images(TR/TE/FA ; 12.3msec/5.9 msec/700) and T1- and T2-weighted spin-echo images. CISS MRimaging findings were evaluated with respect to tumor's signal intensity, contour, and relation with adjacentstructures. Conspicuity of the tumor was compared between CISS and spin-echo images. A quantitative analysis wasperformed by measuring tumor to CSF contrast. In qualitative analysis, three radiologists independently comparedCISS image and conventional spin-echo images for visibility of the tumor and graded them into three categories(poor, good, and excellent). RESULTS: Epidermoid tumors were located in the cerebellopontine angle in 4 cases, theprepontine cisstern in 1 case, and the cerebellopontine angle-prepontine cistern in 1 case. The tumors werehyperintense relative to brain parenchyma and hypointense relative to CSF on CISS images, were lobulated, encasedadjacent cranial nerve and vessels, and invaginated into brain parenchyma. In qualitative analysis, CISS imagesshowed clear demarcation between tumor and CSF, exact tumor extension, and tumor's relation with cranial nervesand vessels better than conventional spin-echo images. In quantitative analysis, the mean contrast values of tumorto CSF on T1-, T2-weighted images, and CISS images were 0.12, 0.06, and 0.52, respectively. The contrast value forCISS images was significantly higher than that for T1- and T2-weighted images (P<0.05) . CONCLUSIONS: Epidermoid tumors in the subarachnoid space are better demonstrated on CISS images than on conventional spin-echoimages. This special MR sequence can be added as a routine protocol in the diagnosis of subarachnoid epidermoidtumor.