Background and aims In the radiologic assessment of ovarian masses, the major difficulty consists in the late recognition and lack of parameters for a differential diagnosis between benign and malignant lesions, especially in the post-menopause when the incidence of cancer is higher. The use of a transvaginal probe and the color-Doppler examination have recently improved the study of the female pelvis. This study is aimed to verify the possibility of the color-Doppler imaging to differentiate between malignant and benign ovarian lesions during transvaginal echographies, on the basis of the qualitative and quantitative characteristics of the vascular pattern of the ovarian lesions.Results Twenty-six expansive ovarian lesions were studied: 8/26 showed no vascular signals and were considered benign as confirmed at histology. In the remaining lesions with some vascularization, the resistance index (RI) was evaluated: those with RI > 0.40 were considered benign, those with RI < 0.40 malignant. In 8/9 benign lesions and in 7/9 malignant neoplasms, the results of color-Doppler were coherent with histology. The results showed a sensibility of 87.5 % and a specificity of 88.8 % for the transvaginal examination.Conclusions The main advantages of the color-Doppler transvaginal examination are: the high frequency of visualization of the ovaries, even in postmenopausal patients; the definition of small lesions; the visualization of small parenchymal vessels, both physiologic and pathologic, and their quantitative analysis. The importance of the RI cutoff was critical for the differential diagnosis between benign and malignant lesions: we think that a cutoff of 0.50, instead of 0.40 proposed by other authors, would be far more appropriate.