Primary hyperparathyroidism is a systemic disease, more and more frequently recognised--concerning 1 to 3% of the population. Statistically appears in 1 of 1000 adults, with significant advantage of women. In Poland every year about 30 new cases are noticed and incidence of it increases with an age. In spite of significant advance of the knowledge, it still makes a lot of diagnostic troubles. It appears to be non-specific illness, characterised by just one symptom, mainly urolithiasis, sometimes chronic ulcer disease, chronic pancreatitis, arterial hypertension, disorders of the movement or psychic disorders. Parathyroid adenoma which is the main reason of the disease is usually single and small, multiple and bigger ones are found exceptionally. In about 2% of cases they are localised in mediastinum. In the comparison to primary hyperparathyroidism the secondary one appears as an effect of the other general disorders. Our material contains 12 patients, 9 with primary and 3 with secondary hyperparathyroidism. All of them were diagnosed and prepared to the operation in the departments of internal diseases. We have not observed any serious complications during the operations and in the postoperative period. In the article the basic symptoms, diagnostic and therapeutic problems of primary and secondary hyperparathyroidism were shown, especially concerning surgical treatment which is safe, radical and efficacious method when performed by experienced surgical team.