Giant parathyroid adenoma (GPA) is defined as adenoma larger than 3.5 g. Twenty-one cases of parathyroid mass >3.5 g in patients with primary hyperparathyroidism who underwent parathyroidectomy in Hospital Putrajaya, Malaysia were identified. Most cases presented with nephrolithiasis. Two cases are reported as parathyroid cancer. GPA has significantly higher serum calcium and iPTH levels and can be asymptomatic. Parathyroid carcinoma patients are frequently symptomatic, with large tumors. Differentiating GPA from parathyroid cancer is important as it determines the subsequent surgical intervention.