We report a rare case of diffuse hepatic hemangiomatosis (DHH) of the left hepatic lobe coexistent with giant hepatic hemangioma and without extra-hepatic involvement in an asymptomatic adult patient. Liver hemangiomas are the most common benign liver tumors. However, DHH without extra-hepatic involvement has rarely been reported in adults. Furthermore, giant hepatic hemangioma coexistent with DHH is even uncommon, although an association between hemangiomatosis and giant hepatic hemangiomas may be supposed. In this peculiar case, we observed an exclusive and widespread involvement of the left hepatic lobe with a sharp boundary between normal and altered liver parenchyma running along Cantlie's line.