Introduction: Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CS/HIPEC) has led to improved survival in select patients with peritoneal surface malignancies. Predicting the volume of disease and any unresectable disease is important for determining CS candidacy. Computed tomography (CT) scan is the preoperative assessment of choice, and diagnostic laparoscopy (DL) is also supported in the literature but has not been widely adopted. In this study, we report our experience comparing and evaluating the role of imaging and DL in the preoperative assessment of patients being considered for CS/HIPEC. Methods: Patients considered for CS/HIPEC at our tertiary cancer center between January 2012 and December 2017 were included. Diagnostic modality sensitivity and specificity were calculated by comparing findings on CT scan and DL to findings at the time of laparotomy and on final pathology. Specificity and sensitivity of the 2 modalities were compared using the McNemar Chi-square test. Results: Our analysis included 71 patients (60.5% male, mean age of 54.9) seen in consultation for CS/HIPEC. Primary cancer diagnosis was 57.7% colorectal cancer, 25.4% pseudomyxoma peritonei, 8.5% mesothelioma, and 8.5% adenocarcinoma of unknown primary. DL was done in 42.3% of patients (median time of 30 days between CT and DL) and an open procedure was done directly after CT in 39.4% (median interval time of 39 days). Findings of DL identified 70% as being unresectable and hence ineligible for HIPEC. The median interval time between 2 operations was 29 days (range, 16–42). When comparing diagnostic modalities to open surgery and final pathology, CT had a sensitivity and specificity of 48.2% and 76.4% and DL, 68.2% and 88.9%, respectively. DL was significantly more sensitive and specific than CT (χ2=5.54; P<.0186) at predicting ascites, small bowel, omental, liver, and lymph node involvement. Conclusion: Our results support the recommendation for performing DL prior to open exploration in patients considered for CS/HIPEC. In our cohort, DL was significantly more sensitive and specific than CT in predicting disease volume and distribution. While there is obviously greater risk to an invasive modality compared to non-invasive CT scan, routine performance of DL can potentially avoid laparotomy without CS/HIPEC in a large proportion of patients. These results will be used to inform the next phase of our study: a prospective clinical trial.