BACKGROUND AND PURPOSE: Differentiation of enhancing malignant lesions on conventional MR imaging can be difficult and various newer imaging techniques have been suggested. Our aim was to evaluate the role of PSR obtained from DSC perfusion measurements in differentiating lymphoma, GBM, and metastases. The effectiveness of PSR was compared with that of rCBV. We hypothesized that the newly defined parameter of PSR is more sensitive and specific in differentiating these lesions. MATERIALS AND METHODS: This retrospective study included 66 patients (39 men and 27 women; age range: 27-82 years) with a pathologically proved diagnosis of primary CNS lymphoma, GBM, or metastases (22 patients in each group). Mean PSR, min PSR, max PSR, and rCBV were calculated. The classification accuracy of these parameters was investigated by using ROC. RESULTS: Mean PSR was high (113.15 ± 41.59) in lymphoma, intermediate in GBM (78.22 ± 14.27), and low in metastases (53.46 ± 12.87) with a P value < .000. F values obtained from 1-way ANOVA analysis for mean, min, and max PSR ratios were 29.9, 39.4, and 23.4, respectively, which were better than those of rCBV (11.1) in differentiating the 3 groups. Max PSR yielded the best ROC characteristics with an Az of 0.934 (95% CI, 0.877-0.99) in differentiating lymphoma from metastases and GBM. The Az for mean and min PSR of 0.938 (95% CI, 0.0.884-0.990) and 0.938 (95% CI, 0.884-0.991), respectively, was better than rCBV (Az, 0.534; 95% CI, 0.391-0.676) in the differentiation of metastases from GBM and lymphoma (P ≤ .0001). CONCLUSIONS: PSR appears to be a parameter that helps in differentiating intracerebral malignant lesions such as GBM, metastases, and lymphoma.