Objectives: The purpose of this study was to compare and evaluate the effectiveness and differences between three diagnostical methods (visual – tactile method, X – ray images and DIAGNOdent device) for detection of occlusal dental caries. Materials and methods: Forty-eight extracted teeth, twelve premolars and thirty-six molars without restorative filling were used in this study (n = 48). The teeth were stored in a 20% hydrogen peroxide solution. Prior to the research the teeth were cleaned and dried to prepare suitable conditions for testing by diagnostic methods. The teeth were stored and numbered in a sponge, and then X – ray images were taken with the Bite-wing technique. Two examiners then diagnosed occlusal dental caries using visual - tactile examination based on ICDAS classification, radiographic examination based on X – ray images and laser fluorescence examination (DIAGNOdent device). Finally, occlusal surfaces of the teeth were microprepared with a diamond bur. The depth of the carious lesions was determined by a dental probe and thus the gold standard was set according to which we compared the tested diagnostic methods. Results: The DIAGNOdent device showed the highest accuracy and sensitivity for detecting occlusal dental caries, followed by radiographic examination and visual – tactile examination that had the lowest sensitivity but the highest specificity. Visual – tactile examination and radiographic examination showed fair to good inter – examiner agreement, while DIAGNOdent device showed poor inter – examiner agreement. Radiographic examination of the Bite – wing images is not a suffiecently reliable method to detect occlusal dental caries. Conclusion: All three diagnostic methods showed deviations from the gold standard method. For successful detection of occlusal dental caries, it is necessary to use combinations of diagnostic methods to make the correct diagnosis as accurately and precisely as possible.