PURPOSE: Magnetic Resonance Imaging (MRI) is widely used for the preoperative staging of breast cancer. In this study, we investigated a role of preoperative breast MRI for detecting the extent of disease and predicting the prognosis of ductal carcinoma in situ (DCIS). METHODS: From January 2002 to April 2008, preoperative MRI was performed for evaluating the extent of disease in 26 patients with DCIS. The MRI findings, the modified Van Nuys scores and the clinicopathological results were reviewed. The accuracy of breast MRI was analyzed with respect to the detection of tumor multiplicity and disease extending into the nipple, and this was compared with that of mammography. RESULTS: For detecting multiple lesions, the sensitivity and specificity of breast MRI were 25.0% and 86.4%, respectively, and the results of mammography were 0.0% and 86.4%, respectively. The accuracy of breast MRI was 76.9% and that of mammography was 73.1%. For detecting tumor extension into the nipple, the sensitivity and specificity of breast MRI was 100.0% and 80.0%, respectively, and that for mammography was 0.0% and 92.0%. respectively. The accuracy of MRI was 80.8% and that for mammography was 88.5%. The MRI final assessment was not associated with the modified Van Nuys score (p=0.474). CONCLUSION: For detecting the disease extent of DCIS, preoperative breast MRI is not superior to mammography due to the low specificity and accuracy of MRI. MRI did not show a definite ability to predict the prognosis of DCIS in this study.