Periportal region is an anatomic space around portal vein comprising hepatic artery, bile duct, nerves, lymphatics and a potential space. Periportal pathologies may involve any of these structures diffusely or focally with characteristic radiologic findings. Radiologic findings can be helpful in differential diagnosis of pathologies of periportal structures including periportal cavernomatous transformation, hepatic artery aneurysm, biliary diseases, neurofibromatosis, lymphoma, langerhans' cell histiocytosis, periportal fatty infiltration and other causes of periportal halo in adult and pediatric patients. Lobar/segmental intrahepatic involvement can be seen in neurofibromatosis, cavernomatous transformation, fatty infiltration and periportal edema. In this review, we discuss CT and MRI findings of periportal pathologies which can be in the form of diffuse or segmental/lobar involvement. (C) 2006 Elsevier Ireland Ltd. All fights reserved.