Diffuse hepatic hemangiomatosis (DHH) is an extremely rare disease, especially in adults. We present a case of DHH involving the entire liver in a 62-year-old male with a giant hemangioma next to the superior mesenteric vein. Based on what we could find in PubMed with pathological evidence, there are only seventeen cases of adult DHH reported in the literature. The female-to-male ratio is 2.4:1. Most patients consult for abdominal pain or distension. Radiographic examination shows multiple diffuse liver nodules. On MRI, these lesions show hypointense T1 and hyperintense T2. Some lesions may show peripheral rim enhancement in the arterial phase but no portovenous washout. In total, 47% of patients with DHH have one or more giant hemangioma(s). Pathology shows that the lesions are lined with flat endothelial cells without cellular atypia, which are stained positive for vascular endothelial markers. Liver failure is the main cause of death. Some patients can be improved by partial hepatectomy. However, there is no effective treatment for most patients. Liver transplantation should be considered in patients with liver failure or congestive heart failure caused by DHH. We attempt to classify DHH into two types based on the distribution of DHH and their treatment.