Background Advanced epithelial ovarian cancer (EOC) often involves the peritoneum. Because complete resection of tumor and carcinosis is the most important prognostic factor, the peritoneal carcinosis index (PCI) has been evaluated in EOC. We hypothesize that specific PCI regions comprising the small intestine with mesentery (regions 9-12) and the hepatoduodenal ligament (region 2) are more predictive of complete resection (R = 0) and survival than the entire PCI. Materials and Methods We analyzed prospectively collected nationwide data from 507 patients with International Federation of Gynecology and Obstetrics stage IIIB to IVB EOC who underwent primary surgery with complete cytoreductive intent. The PCI as a predictor of incomplete resection (R > 0) was evaluated with logistic regression and receiver operating caracteristic curves. Survival analysis was performed with Kaplan-Meier curves and Cox regression. Results Median (range) PCI was 10 (0-33) in R = 0 patients and 24 (1-39) in R > 0 patients; P < 0.0001. The PCI of regions 9 to 12 (odds ratio [OR]:1.38 (1.29-1.47; 95% confidence interval [CI]) and 2 + 9 to 12 (OR: 1.31 [1.24-1.38; 95% CI]) were more predictive of residual tumor than the entire PCI (OR: 1.10 [1.08-1.12; 95% CI]). Similarly, in receiver operating characteristic curve analyses of R greater than 0 versus R = 0, the area under the curve was higher in regions 9 to 12 (78%) and regions 2 + 9 to 12 (79%) than for the total PCI (75%). Median overall survival was 56.8 months (48.3-65.4; 95% CI) after R = 0 and 26.7 months (21.4-32.0; 95% CI) after R greater than 0 (P < 0.0001). Overall survival was 53.8 months for patients with PCI less than median (14) versus 25.7 in patients with PCI greater than median. The PCI in regions 9 to 12 (hazard ratio [HR]: 1.10 [1.07-1.13; 95% CI]) and 2 + 9 to 12 (HR: 1.08 [1.06-1.11; 95% CI]) was associated with a poorer prognosis than the entire PCI (HR: 1.03 [1.02-1.04; 95% CI]). Conclusions Selected PCI regions corresponding to the small intestine and hepatoduodenal ligament are more predictive of complete resection and survival than the entire PCI. This confirms that in the majority of the cases, an early intraoperative examination of those selected PCI regions - and not the entire PCI - will reveal whether R = 0 is achievable.