OBJECTIVE: The aim of our study was to evaluate and compare retrospectively MIBI-dual phase and MIBI/I-123 subtraction scintigraphy for preoperative localisation of hyperfunctioning parathyroid glands. In our department we also attempted to improve the results of the latter method by altering the subtraction technique. SUBJECTS AND METHODOLOGY: Fifty-one patients with hyperparathyroidism underwent preoperative evaluation with radionuclide scanning for the localisation of abnormal parathyroid glands. MIBI-dual phase and MIBI/I-123 subtraction scintigraphy were carried out respectively in fourteen and thirty-seven patients. Anatomopathological findings were used as the gold standard. RESULTS: Topographic identification of the pathological parathyroid glands was correct in 28% for MIBI-dual phase, in 46% for MIBI/I-123 ('old' method) and in 67.5% for MIBI/I-123 ('new' method). Relying on a normal histology of the normal parathyroid glands, there's a specificity of respectively 82.7%, 99% and 96%. CONCLUSION: MIBI/I-123 subtraction scintigraphy is superior to MIBI-dual phase for the preoperative detection and localisation of hyperfunctioning parathyroid tissue, especially when using a gradual subtraction.