This report covers guidance on performance measurements of PET/CT systems. It is intended to be read by scientific staff involved in commissioning, setting up quality assurance programs and providing support for clinical PET/CT services and clinical research. The report aims to define the minimum recommended quality control standards for clinical studies and single and multicentre trials using PET and PET/CT, based on a review of existing practice and consultation with relevant experts. Starting with a brief overview of the physics and technology of PET/CT systems, the report continues with an outline of acquisition techniques and clinical applications. A further chapter focuses on the purchase evaluation and acceptance testing of PET/CT systems along with the requirements for quality control testing. Subsequent chapters address data management, image display and ancillary equipment relevant to PET/CT. Report 108 will be a valuable reference for scientists supporting PET services.