Background: Diagnostic reference levels (DRLs) are optimum range of values or diagnostic standard data for a particular procedure by which other imaging measurements must be compared for purposes of optimizing patient dose and radiation safety in medical imaging. This study aimed to compare measured dosimetric parameters of the latest 640-Slice Aquilion ONE CT scanner with established DRLs for adult and pediatric head, chest and abdominal examinations as a quality assurance test in order to recommend appropriate radiological safety solutions if differences existed. Methods: A prospective and retrospective study design was applied in this work. Data of measured CT dosimetric parameters (patient administered doses) such as dose length product and CT dose index were generated for pediatric head, chest and abdominal examinations using the Aquilion ONE CT scanner. The generated database was compared with established international standard DRLs. SPSS version 16 software was used for data processing and analysis. Results: The measured volume weighted CT dose index (CTDI vol ) and dose length products (DLPs) were generally lower than the ICRP and other internationally recommended DRLs. In particular, the relative deviations from the DRLs were head (CTDI vol = −57.5 %, DLP = −33.8 %, p-value = 0.001), chest (CTDI vol = −94.3 %, DLP = −86.6 %, p-value = 0.002), and abdomen (CTDI vol = −91.0 %, DLP = −75.2 %, p-value = 0.001) for pediatric examinations, and head (CTDI vol = +5. 5 %, DLP = −4.0 %, p-value = 0.001), chest (CTDI vol = −80.3 %, DLP = −56.6 % p-value = 0.001), abdomen (CTDI vol = −6. 8 %, DLP = −54.7 %, p-value = 0.001) for adult examinations respectively. Conclusion: The CTDI vol and DLP administered doses for both pediatric and adult examinations were lower than their respective DRLs except adult head examination where the measured CTDI vol was 5.5 % higher than the standard reference dose. Optimization of practice is needed to reduce dose to head CT examinations when using 640-slice Aquilion ONE CT scanner.