PURPOSE: The peritoneal cancer index (PCI), developed by Sugarbaker in 1990 is a validated tool to quantify extent of peritoneal disease in patients with peritoneal carcinomatosis. It is used to select and prognosticate patients undergoing cytoreductive surgery (CRS) with or without HIPEC. Improvements in perioperative morbidity and long-term survival have resulted in some patients who require repeat or iterative CRS to treat recurrent peritoneal disease. A precise evaluation of PCI by diagnostic laparoscopy is often precluded due to extensive adhesions following initial CRS. As such, greater value is placed on radiological investigations such as CT, MRI and FDG-PET. The aim of this study is to evaluate the accuracy of radiological PCI in peritoneal malignancy patients undergoing repeat CRS. METHODS: A retrospective review of all patients who underwent repeat CRS in a peritoneal malignancy unit from January 2022 to December 2023 was performed. Accuracy of radiological PCI, determined via multidisciplinary meeting involving specialist surgeons and radiologists, was compared to surgical PCI, calculated during the CRS procedure. RESULTS A total of 32 patients were included, of which pseudomyxoma peritonei was the most common histopathology (63%). The median time interval between CRS procedures was 21.5 months. FDG-PET had the highest accuracy (67.5%), followed by CT (62.6%) and MRI (50.0%) in assessing PCI. Completeness of cytoreduction did not significantly correlate to accuracy of radiological PCI. CONCLUSION Radiological PCI for patients undergoing repeat CRS is most accurately predicted by FDG-PET and CT, rather than MRI.