Objectives: Pathologic radiolucencies in periapical radiographs are a sign of bone lesions including cortical plates. Since superimposition is inevitable, it is hard to distinguish whether the buccal or lingual plate is involved. In periapical radiographs, depending on the density of anatomical structures, the image would be on a continuous scale between black and white. Usage of special software in digital radiography makes it possible to show these structures within the broad spectrums of red, blue and green colors, and so it is easier to distinguish different points with different densities. The purpose of this study is to use broad colored spectrums in periapical radiographs in order to investigate involvement of cortical plates in endodontic or periodontal disease. Methods: Cases with definite bone lesions in periapical radiographs were chosen. In all of these cases, distinguishing the involved cortical plate was impossible with clinical examination. Three digital images of front, mesial and distal sides were made. The shift of the tube was 15 inches to each side. Involved cortical plates could be distinguished as the colored bone lesion changed its position according to the SLOB rule. These diagnoses were confirmed during later surgery. Results: Usage of broad colored spectrums gives better visualization of the operation site, so the precise treatment plan can be chosen. Conclusion: Use of the color spectrum in digital radiography could be a predictable technique in diagnosis of periodontal bone lesions.