Objective: This study was designed to evaluate the diagnostic yield of Technetium-99m hexakis methoxyisobutylisonitrile (Tc-99m-MIBI) scintigraphy in patients with primary hyperparathyroidism (PHPT) for identification of the site of parathyroid adenoma compared versus operative and histopathological findings. Patients and Methods: The study included 13 cases with PHPT; 5 males and 8 females with mean age of 56.5±10.3; range: 39-69 years. Preoperative scanning using 99mTc-sestamibi was done. All patients underwent surgical exploration after methylene blue transfusion. Imaging data were compared with intraoperative finding. All identified and excised glands were sent for histopathological examination. Results: Preoperative sestamibi scan defined a case with mediastinal parathyroid gland and another active cervical gland in 2 patients with persistent and recurrent hypercalcaemia, respectively. Preoperative sestamibi scan defined 6 cases with single parathyroid adenoma in each case, while surgical exploration defined 7 parathyroid adenomata; 5 cases had solitary adenoma and one case had adenoma in 2 parathyroid glands both stained blue after methylene blue infusion. Thus, sestamibi scan defined solitary parathyroid adenomas with an accuracy rate of 83.3%. However, sestamibi scan defined 3 cases with adenoma in 2 parathyroid glands and 2 cases had adenoma in 3 glands. Surgical exploration defined adenoma that confirmed histopathologically in 9 glands of the 12 identified by sestamibi scan; 4 cases had 2 adenomas and one case had one solitary adenoma, the other 3 glands showed only hyperplasia without adenoma formation. Thus, sestamibi scan defined multiple parathyroid adenomas with an accuracy rate of 75%. Conclusion: It could be concluded that preoperative localization of parathyroid gland depending on preoperative sestamibi scan could identify ectopic active glands with accuracy 100% and active cervical glands with an overall accuracy rate of 79.2% and concomitant intraoperative methylene blue localization allowed detection of active glands missed by preoperative sestamibi scan.