Abstract OBJECTIVE: To assess the agreement between three-dimensional volume off-line analysis as compared to real-time ultrasound for assessing adnexal masses. STUDY DESIGN: Ninety-nine non-consecutive women diagnosed as having an adnexal mass were assessed by transvaginal power Doppler ultrasound. One single examiner performed all ultrasound examinations. Based on the examiner's subjective evaluation using gray scale and Doppler ultrasound findings a presumptive diagnosis (benign or malignant) was provided after real-time ultrasound was performed. Once real-time was done a 3D volume of the adnexal mass was acquired and stored by this examiner. Two examiners, unaware of the real-time ultrasound results, evaluated the 3D volumes using multiplanar display and virtual navigation and also had to provide a presumptive diagnosis (benign or malignant). These two examiners, like the first one, had information about patient's age, menopausal status and complaints. All women underwent surgery or were followed-up until cyst resolution. Histologic diagnosis was used as gold standard. Cysts that resolved spontaneously were considered as benign for analytical purposes. The Kappa index was used to assess the agreement between real time ultrasound and 3D volume analysis. Sensitivity and specificity of both methods were calculated and compared using McNemar test. RESULTS: Forty-one masses were malignant and 58 were benign. Agreement between real-time ultrasound and 3D volume analysis was good for both off-line examiners (Kappa index: 0.82, 95% CI: 0.70-0.93 and 0.78, 95% CI: 0.65-0.90). Sensitivities for real-time ultrasound and 3D volume analyses were 100%, 93% and 90%, respectively (p>0.05). Specificities for real-time ultrasound and 3D volume analyses were 91%, 84% and 86%, respectively (p>0.05). CONCLUSIONS: Off-line 3D volume analysis may be a useful method for assessing adnexal masses, showing a good agreement with real-time ultrasound and having a similar diagnostic performance.