Summary Aim: Investigation of the diagnostic role of technetium-99m methoxyisobutylisonitrile (99mTc sestamibi) scintimammography in non-palpable, suspicious breast lesions described as microcalcification, mass and increased density using mammography. Patients, method: 35 women with non-palpable breast lesions were enrolled in the study. Anterior, left and right lateral, ipsilateral posterior oblique images were obtained 15 min after the injection of 740 MBq of 99mTc sestamibi. All scintigraphic images were evaluated visually and focal increased 99mTc sestamibi uptake was accepted as malignant lesion. Breast lesions were classified as microcalcification (13 women), mammographic mass (16 women) and increased density (6 women). Excisional biopsy was performed in all of them irrespective of the scintigraphic results. Results: The focally increased 99mTc sestamibi uptake was seen in 11 breast lesions with malignant lesions and in 4 breast lesions with benign lesions. The diffuse uptake of 99mTc sestamibi was seen in 18 breast lesions with benign lesions and 2 breast lesions with malignant lesions. There was no false positive result of 99mTc sestamibi in microcalcification group and there was no false negative result of the mammographic mass and increased density groups. Conclusion: Scintimammography might be a complementary method in decision making for the non-palpable, suspicious breast lesions that were evaluated as microcalcification, mass and increased density mammograpically.