The purpose was to compare the accuracy of multidetector CT (MDCT) on a 16-row CT scanner and magnetic resonance (MR) imaging in the characterization of ovarian masses. Preoperative CT examination of the abdomen and MR imaging of the pelvis was performed in 67 women, with clinically or sonographically detected adnexal masses. The CT examinations were performed on a 16-row CT scanner, and the protocol included scanning of the abdomen during the portal phase, using a detector collimation of 16 x 0.75 mm and a pitch of 1.2. We used a 1.5-T magnet unit to perform T1, T2 and fat-suppressed T1-weighted sequences, before and after intravenous administration of gadolinium chelate compounds. The accuracy of multidetector CT and MR imaging in the differentiation between benign and malignant ovarian masses was evaluated, using histopathologic results as the standard of reference. The sensitivity, specificity and accuracy of MDCT in the characterization of ovarian masses were 90.5%, 93.7% and 92.9%, respectively, and that of MR imaging 95.2%, 98.4% and 97.6%, respectively. Although MRI performed slightly better, this did not reach statistical significance. In conclusion, both MDCT on a 16-row CT scanner and MR imaging demonstrated satisfactory results in the characterization of ovarian masses.