The greatest challenge in dental practice is diagnosing non cavitated dental caries. Diagnostic tools play a very valuable role in the detection of dental caries. In this study traditional radiographic bitewings and the newer DIAGNOcam were used to identify caries lesions. Bitewing radiography enhances the diagnosis of dental caries in areas that are inaccessible to clinical visual inspection by revealing a radiographic image of the lesions that are present. The DIAGNOcam is a form of near infra-red (NIR) transillumination that transmits light through the tooth in order to detect the dental caries lesions. It uses a digital camera to capture images of the lesions, from which the extent of demineralization can be determined. Aim: To compare the reliability of DIAGNOcam to that of bitewing radiography in the detection of proximal dentinal caries in permanent teeth. One hundred eighty-seven teeth were scanned with the DIAGNOcam. Once the DIAGNOcam examinations of the teeth were completed, digital bitewing radiographs were obtained under standardized conditions. The images obtained from the DIAGNOcam and the bitewing radiographs were evaluated by two observers. Statistical analysis was performed to assess the percentage of agreement between the two methods using Statistical Package for Social Sciences (SPSS, IBM, USA); and the inter- and intra-rater reliability were assessed. The findings from the bitewing radiographs of the class IV proximal dentinal lesions were used as a gold standard, and compared to the corresponding NIR light images that showed 97.3% agreement between the two methods in the diagnosis of dentinal caries. Kappa statistics, used for assessing the agreement between the two observers, indicated an inter-rater reliability of 0.978 (p = 0.00001). Cronbach's Alpha, used to assess the intra- reliability of the findings by the main observer, showed 0.987 (p = 0.00001). The results were based on the correlation of bitewing radiographs and DIAGNOcam images according to a selection of positively validated dentin caries lesions. DIAGNOcam might be reliable for detecting proximal dentin caries in permanent teeth. The introduction of NIR light transillumination via the DIAGNOcam allow integration of this imaging procedure into everyday dental practice, which could lead to a reduced usage of radiographic bitewings for the detection of proximal caries. © 2018, University of Dicle.