We have investigated 13 patients with incidentaloma using PET with 11C-metomidate. The patients included six adrenocortical adenomas, one adrenal cancer, two pheochromocytomas, one myelolipoma, one benign cyst and two metastases. A very high tracer uptake was observed in all tumors originating from the adrenal cortex, allowing excellent visualisation, whereas all other processes were negative. PET with 11C-metomidate is a very promising method for the characterisation of incidentalomas and is suggested to be included very early in the evaluation of these patients.