Abstract： Objective To compare the accuracy of cone-beam computed tomography (CBCT) and digital intraoral radiography in the detection of proximal caries.Methods Forty-five non-restored human premolars or molars were selected for the study.The teeth,4 or 5 as a group,were mounted in 11 plaster blocks.The CBCT images of the tooth blocks were acquired with the ProMax 3D and the DCT Pro imaging systems,while the digital intraoral radiographs were obtained by a digital imaging system Digora Optime.Five postgraduates evaluated all the images for carious lesion in the 90 proximal surfaces using a five-level scale.With the histological examination serving as the reference standard,observers' performances were evaluated by receiver operating characteristic (ROC) curves.Results Fifty-eight proximal surfaces were sound,18 had enamel caries and 14 had dentine caries.No significant differences was found among the three modalities for the proximal caries detection ( P =0.186 ).When only the dentine caries was analyzed,significant difference was found between CBCT and digital intraoral radiography (P =0.004).No significant difference was noted when only enamel caries was analyzed (P =0.885 ).Conclusions Although CBCT was better than digital intraoral radiography in the detection accuracy of proximal caries,however,considering the relatively higher radiation dose,CBCT should not be used routinely to diagnose proximal caries in clinic.