Functional imaging plays a key role in the management of NENs. Somatostatin receptor PET/CT imaging has largely replaced Octreoscan where available; FDG PET/CT is increasingly used especially in imaging high-grade NENs, and specific radiotracers are used for insulinomas. PET/CT can predict NEN biology and prognosis, direct treatment planning, and determine the suitability of treatment with peptide radionuclide receptor therapy. Areas of evolving research include the use and interpretation of dual PET in NENs, novel radiotracers, and integration of PET biomarker research into clinical trials.