The aim of this paper is to give the reader an updated overview of (99m)Tc-MIBI SPET applications in investigating brain tumours. Elements determining MIBI uptake at the level of the brain are first mentioned. (99m)Tc-MIBI SPET features in different malignant and benign brain lesions (low and high grade gliomas, glioblastoma multiforme, metastasis, lymphoma, meningioma, neuroma, radiation necrosis and other rarer brain lesions) are reviewed. The ability of 99mTc-MIBI SPET, alone or in combination with other radiotracers, in the differential diagnosis of brain lesions is discussed. We outline (99m)Tc-MIBI SPET value in determining brain tumours grading and in distinguishing tumour recurrence from radiation necrosis. Clinical applications of 99mTc-MIBI in the management of AIDS patients, where discrimination between lymphoma and several different lesions only on the basis of CT or MRI findings is often impossible, are reported. In addition the relationships among (99m)Tc-MIBI SPET, P-glycoprotein (MDR-1 gene product) expression in brain neoplasms and chemotherapy response are mentioned.