The authors investigate the role of MIBI scintigraphy in the early diagnosis of breast cancer. The importance of early diagnosis is emphasized by the fact that breast cancer has the highest morbidity and mortality preceding cervical carcinoma amongst women. Retrospective examinations were made in case of 42 patients operated before because of breast cancer in order to examine accuracy of both mammography and scintigraphy in comparison with the results of histological diagnosis. In these cases sensitivity of scintigraphy turned out to be 69%, while its specificity 42%. In cases of mammographical investigations the sensitivity proved to be 74% and specificity was 61%. Besides mammography, scintigraphy has a very important additional role in the diagnosis of breast cancer. Because of its results and costs scintigraphy is not able to take over the mammography's dominant position (as a popular diagnostic method) but in selected patients' groups it can help to realise tumors as well as to avoid unnecessary operations or needle biopsis. Based on our results this method can give significant additional information in T1b and especially in T1c states of tumors. Therefore this method can be offered as an additional investigation in cases of physically realised or mammographically screened, but not-palpable, larger than 1 cm size lumps when there is little or moderate risk of malignancy.