ObjectiveTo investigate the effect of Yttrium-90 selective internal radiotherapy (90Y-SIRT) on tumor control and compensatory hyperplasia of left hepatic lobe in the treatment of right hepatic malignant tumor. MethodsThe clinical data of 134 patients with liver malignant tumor (primary or secondary) who were treated with 90Y-SIRT in the Department of Hepatobiliary and Pancreatic Surgery, Beijing Tsinghua Changgung Hospital from September 2022 to November 2023 were collected, and 29 patients who met the inclusion and exclusion criteria were analyzed retrospectively. The liver volume, tumor volume, postoperative future liver remnant (FLR) and the percentage of FLR proliferation before and after treatment were measured by CT or MRI, and the surgical resection rate and pathological necrosis rate of tumor focus after 90Y-SIRT treatment were analyzed. The liver volume, tumor volume, postoperative future liver remnant (FLR) and the percentage of FLR hyperplasia were measured by CT or MRI before and 1 and 3 months after 90Y-SIRT, and the surgical resection rate and pathological necrosis rate of tumor lesions after 90Y-SIRT treatment were analyzed. ResultsOf the 29 patients, 22 patients with hepatocellular carcinoma, 2 patients with cholangiocarcinoma and 5 patients with liver metastases from colorectal cancer received 90Y-SIRT of the right liver. At 1 and 3 months after treatment, the tumor volume average decreased by 149.2 mL (P=0.124) and 228.2 mL (P=0.012), the right liver volume was average reduced by 197.4 mL (P=0.026) and 318.6 mL (P=0.023), the left liver volume average increased by 64.9 mL (P=0.261) and 144.7 mL (P=0.124), and the percentage of FLR increased by 6.6% (P=0.018) and 13.4% (P＜0.001) of 29 patients, respectively. Three months after operation, mRECIST standard was used to evaluate the curative effect of tumor imaging. The results showed that the objective response rate of tumor was 79.3% and the disease control rate was 93.1%. Conclusions90Y-SIRT can effectively control the growth of malignant tumors in the right lobe of the liver and induce compensatory hyperplasia of the left liver. At the same time, high objective response rate and pathological necrosis rate of tumor lesions can be obtained.