Purpose In patients with advanced hepatocellular carcinoma (HCC) treated with sorafenib, post-progression survival (PPS) is marked by the pattern of progression. Our aim was to assess the influence of the pattern of progression to selective internal radiotherapy (SIRT) in PPS among patients with HCC. Methods A retrospective analysis of patients treated with SIRT between 2003 and 2015 was conducted, excluding those with a single nodule < 5 cm or with metastases. Four patterns of progression to SIRT were defined: target tumour growth, non-target tumour growth, new intrahepatic disease, and new extrahepatic disease. PPS was calculated from the time of progression based on RECIST 1.1 criteria. Results Out of the 102 patients who met the selection criteria, 76 progressed after a median follow-up of 15 months. Median PPS was 6.5 months (95% CI 3.8-9.3 months). Patients who progressed at pre-existing lesions had a better PPS (median 12.5 months) than those who progressed with new lesions inside or outside the liver (median 4.2 months) (p = 0.02). In a Cox model adjusted by liver function and systemic inflammation, the pattern of progression had a hazard ratio of 1.64 (95% CI 0.92-2.93;p = 0.093). Conclusion In a cohort of HCC patients treated with SIRT, the pattern of progression associated with worst survival was the development of new intrahepatic lesions or extrahepatic metastases.