Abstract: An integrated PET/CT system consists of a positron emission tomography(PET)and a computed tomography(CT)scanner assembled together in the same gantry.It is an imaging modality that combines structure and metabolism.To be cost-effective,PET/CT must be diagnostically accurate and effective in improving management without increasing treatment cost.The acquisition time of PET/CT is shorter than needed for PET along.Moreover,a shorter acquisition time allows a better compliance of the patient,improving patient comfort and reducing possible errors due to movements.The main uses of PET/CT in clinical practice are in oncology, cardiology and neuropsychiatry.With the optimization of the staging procedures and more rapid therapeutic intervention in oncology,PET/CT plays an important rule in the cost-effectiveness.