Hepatocellular carcinoma and metastatic colorectal carcinoma are amongst the more common causes of cancer-related mortality worldwide. Selective internal radiation therapy (SIRT) with 90y microspheres is usually indicated in patients with nonresectable status and extensive colorectal liver metastases that are refractory to chemotherapy or target therapy. Several examinations, including CT, MRI or PET, serum chemical analyses, hepatic angiography and liver-lung shunting study with Tc-99m MAA, are done to ensure appropriateness and safety of therapy. Herein, three cases (two with hepatocellular carcinoma and one with metastatic colorectal cancer), which qualified for SIRT and underwent SPECT-CT, are presented. All of them underwent the necessary pre-therapy work-ups. The CT and PET-CT scans identified the hepatic lesions. The blood tests showed nearly normal hepatic and renal functions, except for the third case with elevated bilirubin level. The hepatic angiograms revealed no significant gastrointestinal shunting. The liver-lung shunting studies computed <20% hepatopulmonary shunt fraction in all cases. One patient had >10% hepatopulmonary shunt. Together with the patient with an elevated bilirubin level, they received a reduced dose of 90Y microspheres by 20%. After SIRT, bremsstrahlung planar imaging and SPECT-CT were performed to localize the distribution of the 90y microspheres, the findings of which correlated well with the results of the pre-therapy scans. The use of SPECT-CT is recommended for better anatomic localization and functional correlation.