The purpose of the study: to assess the possibility of using nuclear medicine techniques at the stages of diagnosis and treatment of breast cancer. Materials and Methods: The study included 290 patients with breast cancer and 70 patients with benign breast tumors. The study was used as a radiopharmaceutical 99m -IBI, 199 l for imaging tumors and colloid 99m -loteh for visualization sentinel lymph nodes (SLN), colloid was injected peritumoral in four points to 80 MBq one day prior to the planned operation. Results: The sensitivity of SPECT using both 99m -IBI and 199 l for breast cancer detection was shown to be rather high, being 98.5% and 98%, respectively. It should be noted that the sensitivity of SPECT in detection of small tumors (less than 1 cm in diameter) and multicentric tumors was not high irrespective of the radioisotope used (60% and 65% with 99m -IBI and 65% and 59% with 199 l, respectively). The difference in the sensitivity was found between 99m -IBI and 199 for the detection of regional lymph node metastasis (91% vs 70%). SLN were detected in 31 patients. The most commonly SLN were defined in the axillary region of 96.7%. In 22 (70.9%) patients there was no metastasis SLN. The sensitivity of the method was 91.2%, specificity of 100%. Conclusion: The specificity of SPECT with 199 l was higher than that with 99m -IBI. The data obtained show that SPECT with 199 l can be recommended for its use as an additional breast cancer detection method in cases when other imaging techniques and histological findings are not accurate enough. The clinical study of 99mloteh, a new radiopharmaceutical agent, has shown that the studied colloid has high uptake level in SLN and can be successfully used for visualization of SLN in patients with breast cancer.