Aim: To evaluate the power of 18F-fluorocholine (FCH) positron emission tomography/magnetic resonance (PET/MR) imaging in primary hyperparathyroidism. Method: Twenty consecutive patients (female: 12, male: 8, mean age: 48.65±14.93) with primary hyperparathyroidism who were referred to Ankara University Faculty of Medicine, Department of Nuclear Medicine for F-18- FCH PET/MR study were included in the study. All patients had previously undergone neck ultrasound (USG) and Tc-99m metoxyisobutylisonitrile (MIBI) scintigraphy but parathyroid adenoma could not be localised. Results: Mean levels of serum PTH and Cancer were: 85±29.9 and 10.7 respectively. 18F-FCH PET/MR was positive for a parathyroid adenoma in 17/23 patients. In 6/17 patients, 18F-FCH PET/computerized tomography (CT) was also found negative. Parathyroid adenoma was surgically excised in 3/17 patients and F-18-FCH PET/MR was confirmed to be true positive by parathormone washout in 2/17 patients. In 12/17 positive cases, patients were clinically accepted as true positive and are now canidates for surgery. Histopathological results could not be obtained due to short follow up period. Conclusion: F-18-FCH PET/MR is an effective method for preoperative localisation of parathyroid adenomas where neck USG and Tc-99m MIBI scintigrapgy are negative. F-18 FCH PET/MR may also be considered as an effective tool in patients whom F-18FCH has also failed. [ABSTRACT FROM AUTHOR]