Introduction : Although bilateral exploration has been thought to be the standard therapeutic modality for primary hyperparathyroidism(pHPT) due to the admirable cure rate, questions have remained as to whether bilateral neck exploration for all patients with pHPT is needed because 80-85% of patients with pHPT have a single parathyroid adenoma. If the diseased parathyroid can be determined preoperatively, a directed and minimal operation is appropriate using the recent innovations of preoperative diagnosis and operation techniques for parathyroid diseases, the radio-guided parathyroid surgery(RGPS) is one of the standards. In especial, RGPS has been reported beneficial in special circumstances, such as in recurrent disease, ectopic parathyroid, and in mediastinal parathyroid. It can be also useful for the parathyroid disease in previously explored or irradiated neck. Material and Methods : We experienced 2 cases of pHPT successfully treated by RGPS in who previously underwent extensive neck dissection and concomitant external or internal radiotherapy. We adopted and modified the technique described by Dr. James Norman at the University of South Florida-the minimally invasive parathyroidectomy using intraoperative nuclear mapping with 99mTc-sestamibi scanning and radioactivity detection probe. Results : We acquired the successful results for these patients. Conclusion : RGPS is thought to be the alternative technique for the patients with prior central neck exploration and irradiation.