Abstract: Two patients with multiglandular disease (MGD) in primary hyperparathyroidism (PHPT) are reported. A total of five lesions were identified intraoperatively, all of which were confirmed as parathyroid adenomas by postoperative histopathological examination. However, preoperative ⁹⁹Tc^m-methoxyisobutylisonitrile SPECT/CT detected only one positive lesion. Both patients presented with elevated serum calcium and parathyroid hormone levels. The authors analyzed the causes of missed diagnosis and conducted a review of the relevant literature based on the clinical manifestations, serum calcium and parathyroid hormone levels, and pathological features of these two patients, aiming to improve the diagnostic accuracy of this disease.