The purpose of this pictorial review is to discuss the usefulness and limitations of diffusion-weighted (DW) MR imaging of the liver, demonstrating DW images of a variety of focal hepatic diseases. We include hepatocellular carcinoma, borderline-lesions in cirrhosis, metastasis, cavernous hemangioma, cyst, focal nodular hyperplasia, hepatic adenoma, abscess, and hematoma. DW imaging is an important supplementary sequence of routine MR imaging protocols of the liver. Radiologists need to understand its usefulness and limitations in the detection and characterization of benign and malignant focal hepatic diseases.