Objective: To analyze the surgical outcomes and diaphragmatic involvement in stage III and IV ovarian cancer. Patients and methods: All patients with stage III-IV ovarian cancer between January 2013 and January 2016 were included. The outcomes of interest reviewed were as follows: surgical (complications, mortality), peritoneal carcinomatosis index (PCI), rate of complete resection, and disease-free interval and survival. Results: Fifty-seven patients were included, 38 (67%) with diaphragmatic involvement; in 10 cases (18%), diaphragmatic resection was required. Optimal cytoreduction (OCR) was obtained in 49 cases (86%). The PCI was 10 in 31 cases (54%). Respiratory complications occurred in 10 cases (18%) and mortality in 3 (5%). Disease-free survival rate in 3 years was 53%, being 87% in cases without diaphragmatic involvement. The overall survival rate in 3 years is 46%, 83% in the cases without diaphragmatic involvement and 27% in cases with affectation (p 0.05). In cases of OCR, 3 year survival rate was 65%. In the multivariate analysis for the overall survival of cases with OCR, the only independent prognostic factor found was the operative PCI. A strong correlation was found between the total PCI and the diaphragmatic PCI (p 0.001). With a PCI 10, virtually all cases will present diaphragmatic involvement (p 0.05). Conclusion: The tumor burden is different in stages III and IV of advanced ovarian cancer and the PCI is an effective method to quantify it. The PCI constitutes an independent prognostic factor for the advanced stages of ovarian cancer. A PCI 10 constitutes a useful prognostic factor of the affectation and forces the surgeon to thoroughly review both diaphragms.