This paper presents an analysis of the results of cytological diagnostics of breast tumors in 3415 patients who underwent tests in the Laboratory of Cytology for 2009-2013. In 1434 patients there were performed cytohistological correlations. Sensitivity of cytology was 99.1%, specificity--93.5%, predictive value of the positive test--98.5%, predictive value of the negative test--95.9%, accuracy--98%. Non-informative material was obtained in 13.5% of cases. The main factors that reduced effectiveness of cytological method were non-informative and little informative material and also difficulties in conducting of differential cytomorphological diagnostics.