With multidetector helical CT, the entire liver can be imaged rapidly with thin slices. High temporal and spatial resolution is important to improve multiphase examinations of the liver. The need to perform multiphase examinations to diagnose benign liver tumors should, however, be assessed by keeping in mind the risk of radiation and contrast-induced adverse events. MRI offers several advantages relative to CT. Excellent contrast resolution is obtained. Multiphase examinations can be performed in all patients. Reticuloendothelial contrast agents may be useful to characterize benign tumors. Several benign liver tumors, particularly hemangiomas and lesions of focal nodular hyperplasia, can be characterized with CT and MRI. Histologic examination is still needed to characterize some benign liver tumors.