The purpose of this study was to describe the appearance on magnetic resonance (MR) imaging of hepatic hemangioma, and how the appearance changes in infants who have received interferon alpha-2a (IFN) treatment. We retrospectively studied 16 MR examinations in seven infants (mean age 3.2 months; range 5 days to 13 months) who were symptomatic with hepatic hemangiomas. Five of these seven patients had MR examinations both before and after treatment with IFN. In six of the seven patients, the hepatic hemangiomas were multicentric; they were usually discrete, well-defined nodules, best seen on T2-weighted images as high intensity lesions. One patient had a large solitary heterogeneous lesion. They all exhibited fast flow (seen as flow voids on spin-echo images and high signal intensity structures on gradient-recalled echo images) and enlarged hepatic arteries and veins. There was enlargement of the proximal abdominal aorta with distal tapering. Treatment was followed by accelerated regression of the hemangiomas in size and number and variable shrinkage of the enlarged vessels. As the tumor nodules regressed, they were replaced by normal-appearing hepatic parenchyma; neither fat nor fibrosis was detected by MR imaging.