Conversion to open surgery might nullify the benefits of laparoscopic surgery. Emergency conversion was associated with significant increases in the postoperative complication rates and length of stay and, more importantly, higher 30- and 90-day mortality rates. Because most of the indications for emergency conversion were related to bleeding or damage to the surrounding structures, conversion is associated with poor short-term outcomes after surgery. Nevertheless, the impact of conversion to open surgery on long-term outcomes remains controversial. Several studies have demonstrated that conversion to open surgery may be associated with adverse long-term oncologic outcomes in laparoscopic colorectal surgery. However, other studies have reported similar oncological outcomes after colectomy between converted and non-converted patients. To date, few studies have investigated the clinical impact of conversion to open surgery compared with LLR. The effects of unplanned conversion (UPC) to open surgery on the survival of patients with hepatocellular carcinoma (HCC) remain controversial. The aim of our study is i) to compare the surgical and oncological outcomes between patients who underwent laparoscopic liver resection (LLR) and those who underwent UPC during LLR for HCC located in posterosuperior (PS) segments. ii) to develop a predictive model for the possibility of UPC using the risk factor for conversion.