OBJECTIVE The purpose of this study was to assess the value of three-dimensional fast imaging with steady-state precession (FISP) MR sequences relative to contrast-enhanced CT and spin-echo MR imaging in the diagnosis of carotid cavernous fistula (CCF). METHODS Seventeen patients with 19 angiographically proved CCFs had contrast-enhanced CT, spin-echo MR imaging, and 3-D FISP imaging. Three observers assessed these imaging studies as well as those of 43 control sides in a blinded manner for the presence or absence of CCF. Receiver operating characteristic analysis was used to assess the diagnostic utility of each imaging technique. In a nonblinded study, contrast-enhanced 3-D FISP images were also evaluated. RESULTS Higher diagnostic accuracy was obtained with 3-D FISP sequences, as the shunt flow within the cavernous sinus was well seen. Sensitivity of 3-D FISP images was 83% and specificity was 100% in the blinded study. In the receiver operating characteristic analysis, the diagnostic performance of observers was found to be better with the 3-D FISP images than with the spin-echo MR images. Although there were no significant difference between 3-D FISP and contrast-enhanced CT, higher diagnostic performance was obtained with 3-D FISP images. In three CCFs without anterior drainage, a diagnosis was made only from the 3-D FISP images. The contrast-enhanced 3-D FISP images were not helpful, since the cavernous sinuses enhanced. CONCLUSIONS Three-dimensional FISP imaging is superior to spin-echo MR imaging and contrast-enhanced CT in the diagnosis of CCF. Contrast-enhanced 3-D FISP images are not helpful for the evaluation of CCF.