Aim: Detection of the primary tumor in CUP-syndrome is one of the most challenging issues in medical imaging but is mandatory for the choice of an adequate therapy. The useful ness of Ga-68 DOTATOC PET in NETs has been demonstrated by many investigators. One of the major disadvantages in the past was the lack of exact anatomic localisation of Ga-68 DOTATOC foci. We investigated the impact of coregistrated Ga-68 DOTATOC PET/CT imaging regarding identification and exact anatomic localisation of primary tumors in CUP-syndrome of NETs. Material and Methods: We investigated 23 consecutive Ga-68 DOTATOC PET/CT examinations of patients with CUP-syndrome of NETs, all of them with liver metastases (confirmed by biopsy from metastatic lesions). All patients were examined with a GE Discovery LS PET/CT scanner 20–40min post injection of 80–120 MBq of Ga-68 DOTATOC. We assessed whether a possible primary tumor could be identifed in the fused images of the combined PET/CT system.