To investigate the efficacy of perfusion magnetic resonance imaging (MRI) in benign-malignant differentiation of thyroid nodules. Images from 24 patients with thyroid masses were obtained using dynamic contrast enhanced MRI (DCE-MRI) at 3-T MR. DCE-MRI images were evaluated by post-processing of selected regions of interest (ROIs) on software, thus eliciting quantitative data for each voxel within the ROI. Ktrans, Ve, Kep, iAUC and chi(2) were calculated automatically. The DCE-MRI values of benign and malignant lesions were then compared. Mean Ktrans and iAUC values in malignant lesions were significantly lower than those in benign lesions (p=0.028 and 0.049). Ktrans, Kep, and iAUC values in malignant lesions were statistically significantly lower than normal parenchyma values. In contrast to other tissues, the perfusion MRI findings of thyroid masses exhibit a decrease in Ktrans and iAUC values as malignancy increases. Perfusion MRI may be useful in differentiating benign and malignant thyroid nodules once a cut-off value has been determined by other studies.