The purpose of this study was to evaluate the contribution of 18F-FDG-PET/CT in highlighting the peritoneal involvement in patients with ovarian cancer, also in relation to the biomarker CA125. We retrospectively analyzed 64 female patients with histological diagnosis of ovarian cancer who underwent 18F-FDG-PET/CT and CA125 measurement. Sensitivity and specificity of 18F-FDG-PET/CT were both 90.63% (95% CI: 80-100%). Sensitivity and specificity of CA125 were 93.33% (95% CI: 80-100%) and 33.33% (95% CI: 25-64%), respectively. In patients with peritoneal carcinomatosis from ovarian cancer, it is recommended to perform 18F-FDG-PET/CT, in particular when elevated CA125 levels are detected.