Purpose : To evaluate accuracy of magnetic resonance(MR) imaging for staging of lung cancer and to compare theaccuracies of CT and MRI. Materials and Methods : We retrospectively analyzed 25 cases of lung cancer, which wereconfirmed surgically and pathologically. Five experienced radiologists participated in the receiver operatingcharacteristic(ROC) analysis to evaluate and compare the accuracies of the CT and MR imaging in preoperativestaging of non small cell lung cancer by assessing tumor invasion of bronchus, mediastinum, chest wall, and hilaror mediastinal lymph node metastasis. Imaging results were evaluated against "truth" data based on both surgeryand pathologic examination. Results : sensitivity of CT in distinguishing T3-T4 tumors was 60%; specificity was76%. These values for MR imaging were not significantly different( 53% and 72%). With ROC analysis, no differenceexisted between accuracies of CT and MR imaging in diagnosis of bronchial involvement, but MR imaging wassignificantly more accurate than CT(p<0.05) in diagnosis of mediastinal invasion. There was no significantdifference between accuracies of CT and MR imaging in detecting mediastinal node metastasis(N2 or N3);sensitivities were 64% and 78%, respectively, and specificites were 64% and 66%. Conclusion : There was nosignificant difference in accuracies of CT and MR imaging in preoperative tumor classification and assessment ofmediastinal node metastasis, but MR imaging was more accurate than CT in assessment of mediastinal invasion. invasion.