INTRODUCTION|Simulation software has aided the estimation of organ dose from computed tomography (CT) examinations. The aim of this study was to use the CT-Expo (SASCRAD, Fritz-Reuter-Weg, Buchholz, Germany) software to determine volume CT dose index (CTDIvol), dose length product (DLP), organ dose and effective dose.¤METHODS|A total of 171 patient data were retrieved from a Toshiba Aquillion 16-slice CT scanner (Toshiba Corp., Tokyo, Japan) representing CT unit A and a Philips Brilliance 16-slice CT scanner (Koninklijke Philips N.V., Amsterdam, Netherlands) representing CT unit B and a CT-Expo spreadsheet was used to estimate the dose delivered.¤RESULTS|Head CT scans were the most frequently seen (64%) at the 2 facilities studied. The CT parameters of peak kilovoltage (kVp) and pitch between the 2 units were statistically different (p<0.05). There was no significant difference in CTDIvol between CT unit A and B (p=0.199). A comparison of CTDIvol and DLP of CT units A and B with other studies revealed no statistically significant difference (p<0.05). The mean effective dose (E) for the abdomen was greater compared with other studies, but without a statistically significant difference (p<0.05). Furthermore, no significant difference in organ dose was seen between CT units A and B (p=0.677). A comparison of organ dose with other studies indicated no relevant difference (p<0.05). ¤DISCUSSION AND CONCLUSION|The CT-Expo software showed good results with the imPACT software (ImPACT scanner evaluation group, London, UK). CT unit A had greater differences in CTDIvol and DLP compared with unit B. This difference could be associated with the significant difference seen in the kVp and pitch of both scanners.¤