Microsphere-based radioembolization represents a new generation of therapeutics in interventional oncology. The intrahepatic application of radioactive microspheres via the hepatic artery allows locoregional therapy of diffuse or multifocal liver tumors, for which to date systemic therapy was the only remaining option. The current standard for this selective internal radiotherapy or radioembolization is yttrium-90 glass or resin microspheres. This review discusses the indications, the technique, and the therapeutic results of microsphere-based radioembolization.