Objective:The aim of this compound cephalometric and arch-width study was to determine arch-width and skeletal differences between subjects with Class Ⅰ normal and with Class Ⅱ division 2 malocclusions.Methods:50 untreated patients’dental models and lateral cephalograms were selected;arch width and tooth width measurements were carried out on study models using a calibrated digital caliper.The radiographs were digitized and processed using WinCeph 8.0 Imaging software

and an independent sample T-test was carried out in order to compare the two groups.Results:The statistically significant differences between the groups for the study model measurements were in maxillary and mandibular intercanine

and interpremolar width.The cephalometric results revealed that ∠SNB and A.P.D.I.ANS-Me

ANS-Me/N-Me(%)

O.D.I.and Pog-NB were different between the two groups.Conclusion:Class Ⅱ division 2 malocclusion patients’ maxillary and mandibular intercanine

and interpremolar width are smaller and they show similar chin prominent

but compared with the Class Ⅰ normal group

the Class Ⅱ division 2 malocclusion patients exhibit mandibular restriction.