Adequate patient selection and treatment planning is crucial for a safe and cost-effective administration of selective internal radiotherapy (SIRT) of malignant liver disease using 90 Y-labelled microspheres. It requires the implementation of multimodality imaging, integrating metabolic, functional and structural characteristics. A multidisciplinary approach is a prerequisite for SIRT, bringing together the knowhow and expertise of radiologists, nuclear medicine physicians, medical physicists, imaging engineers, and radiotherapists. This review discusses the available radiologic (CT/MRI) and nuclear (SPECT/PET) imaging modalities and their specific utility in the different diagnostic phases related to SIRT: wholebody and intrahepatic pre-treatment disease staging, CT and MRI-based angiography, liver-lung shunt assessment, treatment simulation, predictive dosimetry, post-treatment imaging, and SIRT response assessment.