Purpose 18F-fluorocholine PET (FCH PET) is a novel imaging modality for localising parathyroid adenoma(s) in primary hyperparathyroidism (pHPT). European guidelines recommend FCH PET after failure to localise on conventional imaging (US, 4DCT, Tc99m sestamibi). There are no Australian surgical series that have previously evaluated this imaging modality. This study aims to determine the accuracy of FCH PET in parathyroid localisation after negative conventional imaging. Method A prospective study of patients with non-localised pHPT who underwent FCH PET using F-18 Choline 228.3MBq was performed. Baseline characteristics, clinical data and previous imaging results were collected. Accuracy was determined by the correlation of FCH PET, intra-operative location of abnormal parathyroid gland(s) and histopathology. Biochemical cure was assessed with post-operative serum corrected calcium and parathyroid hormone (PTH). Results 17 patients were included (13 women; mean age 60+/-11.1 (SD), pre-operative corrected Ca 2.7+/-0.1mmol/L and PTH 13.2+/-45pmol/L. All had prior negative or equivocal imaging, and 12 patients had persistent or recurrent disease. 12 scans (70.6%) were positive (10 single adenomas, 1 multiple adenomas, 1 metastatic parathyroid cancer) with mean SUV max 7.3+/-3.5. In 5 scans, no lesion was identified. 7 patients localised on FCH PET underwent parathyroidectomy (4 pending) with 9 adenomas (7 ectopic) confirmed on histopathology. 100% were biochemically cured with post-operative corrected Ca 2.3+/-0.1mmol/L and PTH 4.2+/-2pmol/L. Conclusion In this first Australian surgical series FCH PET demonstrates superior sensitivity to US, 4DCT and sestamibi for parathyroid localisation. FCH PET appears to be an effective imaging modality for complex pHPT patients.