Metastatic colorectal cancer (mCRC) is associated with different molecular biology, clinical characteristics and outcome depending on the primary tumor localization. We aimed to evaluate the effectiveness of 90Y-radioembolization (RE) for therapy of colorectal liver metastases depending on the primary tumor side. We performed a retrospective analysis of n=73 patients with mCRC and RE in our university liver center between 2009 and 2018. Patients were stratified according to the primary tumor side (left vs. right hemicolon), treatment response was assessed by the Response Evaluation Criteria in Solid Tumors (RECIST) at follow-up after 3 months. Kaplan-Meier analysis was performed to analyze survival followed by Cox regression to determine independent prognostic factors for survival. Prior to RE all patients had received systemic therapy, with either stable or progressive disease, but no partial or complete response. In n=22/73 (30.1%) patients the primary tumor side was in the right colon, in n=51/73 (69.9%) patients in the left colon. Hepatic tumor burden was ≤25% in n=36/73 (49.3%) patients and >25% in n=37/73 (50.7%) patients. At 3 months, n=21 (33.8%) patients showed treatment response [n=2 (3.2%) complete response, n=19 (30.6%) partial response], n=13 (21.0%) stable disease, and n=28 (45.2%) progressive disease after RE. The median survival in case of primary tumor side in the left colon was significantly higher than for primary tumors in the right colon (8.7 vs. 6.0 months, p=0.033). The median survival for a hepatic tumor burden ≤25% was significantly higher compared with >25% (13.9 vs. 4.3 months, p<0.001). The median overall survival was 6.1 months. The median survival after RE in hepatic-metastatic CRC depends on the primary tumor side and the pre-procedural hepatic tumor burden.© 2020 S. Karger AG, Basel.