In Tc-99m MIBI scintimammography, the exact localization of foci of increased tracer uptake or the exact anatomic correlation of palpated breast masses with a scintigraphic finding is difficult. The authors describe three patients with known or possible malignant breast lesions for whom the use of external radioactive markers successfully helped to provide this information, thus improving the diagnostic accuracy and guiding decision-making in the patients' treatment.