In this paper, the ^99mTc-octreotide scintimammography as a useful complementary technique of mammography was evaluated in diagnosing breast cancers. The 45 breast lesions were consecutively detected by mammography, and ^99mTc-octreotide scintimammography, and both combination technique on the basis of self-examination, physical examination. Clinical diagnosis was confirmed by histopathologic analysis. Radioactivity uptake ratios for tumor vs normal breast tissues (T/NT) were calculated using regions of interest. In the breast cancer groups and the benign lesion groups, the average uptake ratios of the ^99mTc-octreotide were 1.63±0.19 and 1.09±0.13, respectively, and t was 9.638 (P<0.001). Based on sensitivity, specificity, accuracy, positive predicting value, and negative predicting value, ^99mTc-octreotide scintimammography was 87%, 79%, 84%, 90%, and 73%, the mammography was 65%, 64%, 64%, 80%, and 45%, and both combination was 95%, 100%, 97%, 100% and 92%, respectively. This showed that the ^99mTc-octreotide scintimammography was more useful than mammography in the evaluating suspected breast cancers, and the combination technique can accurately discriminate lesions.