Overview: Preoperative differential diagnosis of adnexal masses has been a challenge for researchers for years. Prediction of tumor malignancy is essential for selection of optimal treatment with lowest risk for patient. Assessment of various tumor vascularization attributes, using color Doppler semi-quantitative analysis, can be helpful for malignancy differentiation. Objectives: To assess value of selected vascularization attributes of adnexal masses in preoperative prediction of tumor malignancy. Materials and Methods: This study included 521 women diagnosed and treated for adnexal masses (181 malignant and 340 benign) in Obstetrics and Gynecology Hospital of University of Medical Sciences in Poznan between 1994 and 2004. All of them underwent color Doppler examination using Aloka 2000 and 5500 devices (vaginal probes 5,0-6,5 MHz, abdominal probes 3,5-5 MHz) with evaluation of such attributes as: vessels count, localization and structure; semi-quantitative scale was also constructed basing on these parameters. Results: There was a significantly higher number of vessels (cut-off value=4; p<0,0001), central vessels localization (p<0,0001) and irregular structure of vessels (p<0,0001) in patients with confirmed malignant tumor. Constructed semi-quantitative Doppler scale resulted in highest diagnostic accuracy (cut-off value=3; p<0,0001). Conclusions: Central vessels localization was the single most significant attribute in tumor malignancy differentiation. Constructed semi-quantitative Doppler scale resulted in highest diagnostic accuracy and can be a useful tool in preoperative prediction of tumormalignancy.