METHODS A 51-year-old woman was admitted from a mental institution for evaluation of hypercalcemia. She was treated with lithium for a bipolar disorder since 25 years. She complained of polydypsia and polyuria. The physical examination findings were unremarkable up to manic symptoms. METHODS Laboratory values showed elevated serum calcium and parathormone. Serum phosporus was within the normal range. Neck ultrasound revealed a goiter with one nodule in the right thyroid lobe and a suspected enlarged lower left parathyroid gland. The sesta-MIBI-scan failed to detect an adenoma. METHODS In light of long-term treatment with lithium and negative MIBI-scan, lithium-associated- hyperparathyreoidism (LAH) was suspected. The patient refused further preoperative imaging studies, such as c-11 methionine positron emission tomography and thyroid scan. Until surgery after stabilization of the psychiatric condition, treatment with the calcimimetic cinacalcet was initiated. CONCLUSIONS Long-term lithium therapy is frequently associated with LAH. The criteria of diagnosis and therapy are similar to those of primary hyperparathyroidism. Lithium alters the set-point of the calcium-sensing-receptor and results in elevation of parathormone und hyperplasia of the parathyroid glands. Patient with LAH have a higher prevalence of multiglandular disease compared with sporadic hyperparathyreoidism. Thus, the preoperative localization is challenging. After surgery recurrent or resistant disease is more frequent. The calcimimetic cinacalcet is a potential alternative for patients who have contraindications to surgery, refuse surgery, or experience recurrent disease after surgery.