Objectives: The aim of this study was to evaluate the influence of restorative materials on false-positive diagnoses of secondary caries using three imaging systems. Methods: Class II preparations were made on the occlusal and mesial or distal faces of extracted healthy third molar teeth. The teeth were divided into five groups and, with the exception of Group 5, they received a flow resin base. Groups 1, 2, 3 and 4 received a layer of Natural Flow (DFL, Rio de Janeiro, Brazil), Filtek Flow (3M-ESPE, St. Paul, MN), Tetric Flow (Ivoclar/Vivadent, Liechtenstein, Germany) and Protect Liner F (Kuraray, Okayama, Japan) resins, respectively, and were restored with Filtek Supreme resin (3M-ESPE). Group 5 was restored with Filtek Supreme resin. The images on film and on the Digora OptimeH (Helsinki, Finland) and charge coupled device (CCD) IOX (IOX, Monninkylä , Finland) digital systems were evaluated by five examiners and the data were analysed using the Fisher's exact and Friedman tests at a 5% level of significance. Results: Group 3 showed the highest rate of correct answers (restored tooth) and the lowest proportion of secondary caries diagnosis (P # 0.05). Group 4 showed the highest rate of secondary caries diagnosis and the lowest proportion of correct answers (P # 0.05). The systems for obtaining images presented were similar for each material. Conclusons: The restorative material was found to have an influence on the diagnosis of secondary caries lesions by imaging. The imaging system had no influence. Materials with greater radiopacity, higher than that of enamel, were favourable for a true-negative diagnosis.