INTRODUCTION: Properly planned and performed diagnostic tests allow the optimal treatment option to be chosen for the patient. They also allow qualification for the correct surgical procedure. AIM OF THE STUDY: In this study we evaluated the clinical value of preoperative ultrasound scan (USS) testing performed during primary disease staging in patients with early breast cancer qualified to sentinel lymph node biopsy (SLNB). MATERIAL AND METHODS: The group of breast cancer patients who underwent SLNB from March 2012 to May 2013. As well as the standard procedure of the preoperative diagnostics model, in each patient the USS of axillary lymph nodes was performed additionally. The results were compared with the data from postoperative pathological reports. We attempted to define the factors influencing the possibility of obtaining false positive and false negative USS results. RESULTS: The analysis comprised 172 patients. In 14.4% of cases with normal USS result the pathological result was different from the expected one (pN1). In 42.3% of patients with suspicious axillary lymph nodes the result of the pathological report was positive. The sensitivity of the USS testing was 89.3%, and the specificity was 34.4%, PPV - 85.6%, NPV - 42.3%. CONCLUSIONS: Ultrasonographic assessment of axillary lymph nodes in breast cancer patients qualified for SLNB is a test with high sensitivity and high predictive value of the positive test result. The possibility of a result contrary to the actual nodal status may result primarily from the technical limitations of USS testing.