Purpose of investigation: To evaluate the diagnostic accuracy of three-dimensional ultrasound (3D-US) and three-dimensional power-Doppler (3DPD-US) as adjuncts to conventional B-mode-US in evaluation of complex benign ovarian lesions. Methods: Transvaginal B-mode-US, 3D-US and 3DPD-US were performed in 29 patients with unilateral ovarian lesion. Patients were classified as low or high risk for malignancy according to a standardized scoring system composed of ten morphological and vascular parameters. Preoperative scores were matched to the histological results and the diagnostic performance of the scoring system was calculated. Results: Seven out of the 16 cases of endometriomas (44%) were graded as low risk masses according to B-mode-US, while the addition of 3D-US and 3DPD-US increased the accuracy to 56% and 94%, respectively. All dermoid cysts were classified as high risk cases by B-mode-US, but 3D-US and 3DPD-US correctly classified 14% and 57% of cases, respectively. The use of B-mode-US, 3D-US and 3DPD-US correctly classified all four cystadenomas. Only the use of 3DPD-US correctly classified one out of two hemorrhagic corpus luteum cases, whereas the other imaging modalities characterized these lesions as high risk. The overall diagnostic accuracy increased from 38%, 48%, and 83% with the application of B-mode-US alone, or combined with 3DUS and 3DPD-US, respectively. Conclusion: Conventional ultrasound supplemented with 3D-US and 3DPD-US and the evaluation of findings according to a specific scoring system can facilitate the preoperative classification of complex benign ovarian lesions.