The effectiveness of using some ratios in ^99mTc-MIBI imaging for the diagnosis of breast tumors was evaluated. After 100 patients with the breast tumor underwent ^99mTc-MIBI imaging, the ratios of tumor to contralateral uptake (T/N). tumor to heart uptake (T/H), and tumor to sternum uptake (T/S) were obtained and then analysed about their reproducibility and values in differentiating benign breast lesion the from malignant tumor. To detect breast cancers, the sensitivity, specificity and accuracy of T/N were 92%, 90% and 91%, respectively. However, those of T/S were 70% (p<0.01), 74% (p<0.05), 72% (p<0.01), and those of T/H were 74% (p<0.05), 76% (p>0.05), 75% (p<0.01). The average coefficients of variation(CV) of T/N. T/S and T/H were 9.439±9.712, 4.856±4.420 (p>0.05), and 3.736±3.489 (p<0.05). It was found that T/N had the best sensitivity, specificity and accuracy to detect the breast cancer, but its reproducibility is poor. On the other hand. T/H has better reproducibility.