Insulinomas are the most common functioning neuroendocrine neoplasms of the pancreas, typically diagnosed due to characteristic symptoms. In the vast majority, the treatment is surgical and curative, requiring accurate localization of the tumour; conventional imaging, including somatostatin receptor molecular imaging, is negative in up to 10 % of cases. Recently, labelled glucagon-like peptide receptor (GLP-1R) analogues were introduced as a sensitive diagnostic method for localization of insulinomas. The aim of this study was to assess the diagnostic accuracy of a Tc-99m-labelled GLP-1R agonist [LysEight patients (all females; age range 35-75 years) with biochemically proven insulinoma and with negative or inconclusive conventional imaging (consisting of somatostatin receptor scintigraphy, computed tomography, endoscopic ultrasound and magnetic resonance imaging) were enrolled. Whole-body single-photon emission tomography/computed tomography (SPECT/CT) imaging was performed 4 h post-injection of 740 MBq of [LysFocal uptake of [Lys[Lys