Objective: To compare the diagnostic performance of ultrasound and computed tomography (CT) for detecting pelvic and abdominal tumor spread in women with epithelial ovarian cancer. Methods: An observational cohort study of 93 patients (mean age 57.6 years) with an ultrasound diagnosis of adnexal mass suspected of malignancy and confirmed histologically as epithelial ovarian cancer was undertaken. In all cases, transvaginal and transabdominal ultrasound as well as CT scans were performed to assess the extent of the disease within the pelvis and abdomen prior to surgery. The exploration was systematic, analyzing 12 anatomical areas. All patients underwent surgical staging and/or cytoreductive surgery with an initial laparoscopy for assessing resectability. The surgical and pathological findings were considered as the 'reference standard'. Sensitivity and specificity of ultrasound and CT scanning were calculated for the different anatomical areas and compared using the McNemar test. Agreement between ultrasound and CT staging and the surgical stage was estimated using the weighted kappa index. Results: The tumorous stage was International Federation of Gynecology and Obstetrics (FIGO) stage I in 26 cases, stage II in 11 cases, stage III in 47 cases, and stage IV in nine cases. Excluding stages I and IIA cases (n=30), R0 (no macroscopic residual disease) was achieved in 36 women (62.2%), R1 (macroscopic residual disease <1cm) was achieved in 13 women (25.0%), and R2 (macroscopic residual disease >1cm) debulking surgery occurred in three women (5.8%). Eleven patients (11.8%) were considered not suitable for optimal debulking surgery during laparoscopic assessment. Overall sensitivity of ultrasound and CT for detecting disease was 70.3% and 60.1%, respectively, and specificity was 97.8% and 93.7%, respectively. The agreement between radiological stage and surgical stage for ultrasound (kappa index 0.69) and CT (kappa index 0.70) was good for both techniques. Overall accuracy to determine tumor stage was 71% for ultrasound and 75% for CT. Conclusion: Detailed ultrasound examination renders a similar diagnostic performance to CT for assessing pelvic/abdominal tumor spread in women with epithelial ovarian cancer.