The Diagnostic Reference Levels (DRLs) are important operational agents for improvement of patient protection from radiation doses in radiological imaging. It advised by the International Commission on Radiological Protection (ICRP) as an advisory measure to optimization of patient protection by determining high patient dose levels which might not be necessary on the basis of image quality needs, so one of the main goals of this study was protection of patients from radiation doses during CT examination, evaluate radiation doses received by patients from CT examination that conducting in three medical imaging centres, Department of radiology in PAR Hospital, Hawler Hospital, and Cardiac Centre, in Erbil.