Peritoneal Cancer Index (PCI) has been recognized as an independent prognostic indicator for long-term outcomes. It also influences the likelihood of complete cytoreduction, another principal determinant of long-term survival. The objective of this study was to evaluate the utility of preoperative CT in estimating PCI during the patient selection process. The efficacy of CT in demonstrating peritoneal disease was evaluated by comparing the radiological and intraoperative lesion size and PCI scores using the Wilcoxon signed-rank test. Tumor distribution was assessed in each abdominopelvic region as tumor present versus absent. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated in each abdominopelvic region. Overall, where CT identifies the presence of disease, it portrayed lesion size accurately in 60%, underestimated in 33%, and overestimated in 7% of cases. Analysis of individual abdominopelvic regions demonstrated a statistically significant difference between radiologically and intraoperatively visualized lesion sizes (P < 0.05) except in the epigastrium, left upper, and left flank regions. The sensitivity of CT in detecting peritoneal implants was influenced by lesion size. Small nodules (<0.5 cm) were visualized on CT with only a sensitivity of 11%, which is in contrast to 94% with nodules exceeding 5 cm. Radiological PCI scores significantly underestimated intraoperative PCI (P < 0.001). This study demonstrated that the sensitivity of CT in detecting peritoneal implants was influenced by lesion size and CT PCI significantly underestimated clinical PCI. The role of CT in refining patient selection and improving prognosis remains to be closely evaluated.