Background: Primary hyperparathyroidism (pHPT) is caused by benign and malignant conditions. Most commonly by typical adenoma/single gland disease (PA) - this is 80-85% cases of pHPT. Parathyroid hyperplasia or multiple gland disease accounts for 10-15% of cases of PHPT. Atypical parathyroid adenoma (APA) and carcinoma (PC) - very rare conditions - are both responsible for pHPT in approximately 0,5 - 1,5% of cases. Objectives: To estimate occurrence of atypical parathyroid adenoma, parathyroid carcinoma and parathyroid hyperplasia along with characterize them based on their etiology, clinical presentation, diagnosis and treatment. Methods: We performed a retrospective study and enrolled 1,019 patients with primary hyperparathyroidism undergoing parathyroidectomy at academic Department of General and Endocrine Surgery between 1983 and 2018. Results: Out of 1,019 cases of primary hyperparathyroidism, 850 (83.4%) cases were due to typical parathyroid adenoma (PA), 135 (13.2%) cases were due to parathyroid hyperplasia, 29 (2.8%) cases were due to parathyroid carcinoma (PC), and 5 (0.5%) cases were due to atypical parathyroid adenoma (APA).