**Objective**: The aim of the present study was to compare relative contribution of apparent diffusion coefficient (ADC) values and ADC ratios (ADC of the lesion/ADC of the neighboring hepatic parenchyma) in the differential diagnosis of benign and malignant focal hepatic lesions.

Methods: A total of 80 patients with 94 focal hepatic mass lesions (mean size, 5.3 cm; range, 1–12 cm) were evaluated retrospectively using 3 Tesla magnetic resonance imaging (MRI). The ADC values and ADC ratios were compared for different types of lesions to obtain ideal cut-off values.

Results: Mean ADC values (±SD) were 0.93±0.15, 0.95±0.48, 1.44±0.39, 1.88±0.50, and 2.94±0.75×10−3 mm2/sec respectively for hepatocellular carcinoma (HCC), metastasis, focal nodular hyperplasia (FNH), hemangioma, and cysts with a mean ADC value of 1.97±0.68 for benign lesions and 0.94±0.29×10−3 mm2/sec for malignant lesions. The ADC ratios of benign and malignant lesions were 1.50±0.53 and 0.80±0.20×10−3 mm2/sec, respectively, and the ADC values and ratios were found to differ significantly between benign and malignant lesions. Assuming a cut-off ADC value of 1.26×10−3 mm2/sec for discrimination of benign and malignant lesions provided 94% sensitivity and 92% specificity. Sensitivity of 85% and specificity of 92% were found when a cut-off ADC ratio of 0.90×10−3 mm2/sec was used for discrimination of benign and malignant lesions. Compared to ADC values, ADC ratios were found to have lower sensitivity and higher specificity for discriminating between benign and malignant lesions.

Conclusion: Diffusion weighted imaging is used in combination with conventional MRI, and it enhances the diagnostic accuracy of MRI in the characterization of benign and malignant lesions.