The purpose of this study was to compare dual-phase spiral computed tomography (CT) and magnetic resonance imaging (MRI) using dynamic gadolinium enhancement for liver lesion detection and characterization. Twenty-two consecutive patients underwent dual-phase spiral CT and MRI for the evaluation of focal liver disease within a 1-month period. Spiral CT and MR images were interpreted prospectively, in a blinded fashion by separate, individual, experienced investigators, to determine lesion detection and characterization. Liver lesions were confirmed by surgery and pathology in 6 patients, and by clinical and imaging follow-up in the other 16 patients. Pathological correlation of a primary extrahepatic malignancy was available in 5 of the 16 patients who had metastatic liver disease. Spiral CT and MRI detected 53 and 63 lesions, and characterized 39 and 62 true positive lesions, respectively. A kappa statistic test was applied to assess agreement between MR and CT results. MR versus CT for lesion detection resulted in a kappa statistic of 0.54 (95% confidence interval), indicating moderate agreement, and 0.32 (95% confidence interval) for lesion characterization, indicating only slight agreement. More lesions were detected on MR images than CT images in 6 (27%) patients, with lesions detected only on MR images in 4 (18%) patients. More lesions were characterized on MR images in 9 (41%) patients. In 9 patients with a discrepancy between MR and CT findings, the MR images added information considered significant to patient management in all 9 cases. MRI was moderately superior to dual-phase spiral CT for lesion detection, and was markedly superior for lesion characterization, with these differences having clinical significance.