The incidence of hepatocellular carcinoma is increasing. Most patients present beyond potentially curative options and are usually affected by underlying cirrhosis. In this scenario, trans-arterial therapies, such as radioembolization, are rapidly gaining acceptance as a potential therapy for hepatocellular carcinoma and liver metastases. Radioembolization is a catheter-based liver-directed therapy that involves injection of micron-sized embolic particles loaded with a radioisotope by use of percutaneous transarterial techniques. Cancer cells are preferentially supplied by arterial blood and normal hepatocytes by portal venous blood; radioembolization therefore specifically targets tumor cells with a high dose of lethal radiation and spares healthy hepatocytes.