Introduction: The aim of the study was to retrospectively define specific features of the technetium-99m pentavalent dimercaptosuccinic acid (^99mTc-(V)DMSA) and technetium-99m 2-methoxy isobutyl isonitrile (^99mTc-Sestamibi [^99mTc-MIBI]) distribution in ductal breast carcinoma in situ and lobular breast carcinoma in situ (DCIS/LCIS), in relation to mammographic, histological and immunohistochemical parameters. Materials and methods: One hundred and two patients with suspicious palpation or mammographic findings were submitted preoperatively to scintimammography (a total of 72 patients with ^99mTc-(V)DMSA and a total of 75 patients with ^99mTc-Sestamibi, 45 patients receiving both radiotracers). Images were acquired at 10 min and 60 min, and were evaluated for a pattern of diffuse radiotracer accumulation. The tumor-to-background ratios were correlated (T-pair test) with mammographic, histological and immunohistochemical characteristics. Results: Histology confirmed malignancy in 46/102 patients: 20/46 patients had DCIS/LCIS, with or without coexistent invasive lesions, and 26/46 patients had isolated invasive carcinomas. Diffuse ^99mTc-(V)DMSA accumulation was noticed in 18/19 cases and ^99mTc-Sestamibi in 6/13 DCIS/LCIS cases. Epithelial hyperplasia demonstrated a similar accumulation pattern. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value for each tracer were calculated. Solely for ^99mTc-(V)DMSA, the tumor-to-background ratio was significantly higher at 60 min than at 10 min and the diffuse uptake was significantly associated with suspicious microcalcifications, with the cell proliferation index ≥ 40% and with c-erbB-2 ≥ 10%. Conclusion: ^99mTc-(V)DMSA showed high sensitivity and ^99mTc-Sestamibi showed high specificity in detecting in situ breast carcinoma (^99mTc-(V)DMSA especially in cases with increased cell proliferation), and these radiotracers could provide clinicians with preoperative information not always obtainable by mammography.