BACKGROUND: To evaluate the value of diffusion-weighted imaging (DWI) for distinguishing between benign and malignant renal masses. MATERIAL AND METHODS: Seventy-five patients with 75 unilateral renal lesions were included, and 75 normal contralateral kidneys served as controls. The lesions were categorized into four groups as malignant cystic, malignant solid, benign cystic and benign solid. The apparent diffusion coefficients (ADCs) were evaluated for two different b values (b=600 s/mm² and b=1000 s/mm²). Receiving operating characteristic analysis was performed to identify threshold ADCs. RESULTS: Sensitivity and specificity were 67% and 77% (p=0.003) at the cutoff value of 1.5 for b=600 s/mm², and 79% and 62% (p=0.004) at the cutoff value of 1.99 for b=1000 s/mm² as regards the differentiation between solid benign and malignant renal lesions. Sensitivity and specificity were 78% and 79% (p=0.001) at the cutoff value of 3.1 for b=600 s/mm², and 86% and 61% (p=0.003) at the cutoff value of 2.9 for b=1000 s/mm² as regrads the differentiation between benign and malignant cystic renal lesions. CONCLUSIONS: DWI can be an effective diagnostic method for distinguishing between benign and malignant renal masses.