Background: Locally advanced HCC (beyond BCLC A, including PVT but without extra-hepatic metastases) that are unresectable because of inadequate future liver remnant may be downstaged by selective internal radiation therapy (SIRT) with Yttrium-90 to subsequently receive interval surgical resection. We hypothesized that HCC that required downstaging before resection will have some disparity in overall survival (OS) and recurrence-free survival (RFS) compared to HCCs that were resected upfront. Methods: We reviewed all patients who underwent surgical resection for HCC between 1^st January 2000 and 31^st December 2019 and identified those that had locally advanced HCC and were downstaged with Y90-SIRT and referred for consideration of surgical resection. OS and RFS of patients resected upfront for early and locally advanced HCC and those resected after downstaging were obtained using the Kaplan Meier method and compared using Log-rank (Mantel-Cox) test after propensity score matching. Results: 1141 patients had surgical resection for HCC within the study period. 245 patients were excluded for other primary cancers or metastatic disease at diagnosis. 875 were resected upfront (473 early, 402 locally advanced) and 23 locally advanced HCC were downstaged with SIRT before resection. Locally advanced HCC patients downstaged with Y90 before resection have significantly better OS and RFS than locally advanced HCC with upfront resection (5-year OS of 69.0% versus 47.5% p = 0.048; 5-year RFS of 53.5% vs 27.0%, p = 0.047) and similar OS and RFS with resected early HCC (5-year OS of 69.0% versus 62.6% p=0.475; 5-year RFS of 53.5% vs 39.0%, p = 0.736). Conclusions: In addition to downstaging HCC to resection, Y90-SIRT also produces a change in tumour biology that favours better prognosis. A randomised controlled trial to the role of SIRT as neoadjuvant therapy in locally advanced HCC is justified and can potentially change practice.