For IPPNET, surgical removal of the tumour is the therapy of choice and is considered curative in case of a benign tumour. Optimal preoperative localization of the lesion is warranted in order to reduce morbidity by helping to optimize the surgical procedure. Successful preoperative localization of IPPNET is a challenging problem since approximately 30% of IPPNET cannot be visualized using the conventional imaging techniques CT and/or MRI and endoscopic ultrasound. Selective arterial stimulation with calcium with simultaneous venous sampling (ASVS) has been described to have a sensitivity and specificity of almost 90% in identifying IPPNET. This is, however, an invasive technique which is accompanied by an risk for complications. Functional imaging with somatostatin (sst) receptor scintigraphy (SRS) and SPECT/CT are able to detect less than 50% of benign IPPNET because of low or absent expression of sst receptor subtypes 2 and 5, which bind octreotide with high affinity. PET with 68Ga-labeled sst analogs has a higher sensitivity for smaller lesions than SRS. Also 11C-5-HTP and 18F-DOPA, which are used as PET tracers for the detection of IPPNET in some centers may be more sensitive than SRS and CT with 11C-5-HTP showing the most accurate visualization. However, when compared to intra-operative findings, 2 out of 6 IPPNET could still not be detected preoperatively. Palpation and intra-operative ultrasound will allow identifying the lesion in approximately 70-80% of cases. However, it remains a challenge to find small or multiple tumours in the pancreas and partial pancreatectomy is frequently required, especially if the lesion is located close to the pancreatic duct. Precise preoperative localization of the IPPNET is therefore critical to minimize surgical intervention. If no IPPNET can be identified pre- or perioperatively, the diagnosis of nesidioblastosis may be established by resection and histopathologic evaluation of the pancreatic tail. If nesidioblastosis is present, partial pancreatectomy is required; the challenge is to remove enough tissue in order to avoid hypoglycaemia while keeping enough functional endocrine pancreatic tissue so that the patient does not become diabetic. Currently, with the risk of reoperation being considered lower than the consequences and complications of diabetes, surgeons usually choose a fairly conservative approach.