Objectives: Currently transvaginal ultrasonography is the most effective method for ovarian tumor malignancy prediction. The aim of the study was to estimate the risk of false negative results in subjective interpretation of the ultrasound examination of ovarian tumors according to menopausal status. Material and methods: 318 women (210 pre and 108 post menopause) with adnexal masses were diagnosed preoperatively between 2004 and 2010. Subjective assessment of tumor characteristics was conducted by experienced ultrasound examiner. Tumors were divided into groups of: “certainly benign” (n=84), “probably benign” (n=116), “uncertain” (n=61), “probably malignant” (n=47), and “certainly malignant” (n=10). The percentage of false negative results was calculated among the first two groups according to menopausal status. Results: There were 91 malignant and 227 benign adnexal masses diagnosed in histopathological evaluation. There was one false negative result of subjective interpretation of ultrasound findings in postmenopausal women – 1.6% (1/64). She was a 63-year-old woman with bilateral solid ovaries sized: 4.2x3.1cm and 4.6x2.5 cm in ultrasound evaluation, where serous adenocarcinoma was diagnosed. There were three false negative results in premenopausal women – 2.2% (3/136). The first was a 34-year-old woman with a cyst with the appearance of ground glass of 19 x11cm in size where endometrioid ovarian adenocarcinoma was diagnosed. The second woman was a 32-year-old with a bilocular cyst 8x4.5cm diagnosed with borderline mucinous tumor. The third patient was a 21-year-old woman with unilocular-solid cyst 4.2x3.2cm where histopathological examination revealed borderline serous tumor. Conclusions: Subjective ultrasound evaluation of adnexal masses has high specificity but even in the group of tumors considered benign in premenopausal as well as postmenopausal women malignancy can be found. This occurs slightly more often before menopause.