To compare the ability of endodontists to determine the size of apical pathological lesions and select the most appropriate choice of treatment based on lesions' projected image characteristics using two dimensional and three dimensional images. Study Design: Seven subjects were selected. Radiographic examination of symptomatic study teeth with an intraoral periapical radiograph and Radiovisiography (RVG) revealed periapical lesions equal to or greater than 3mmin the greatest diameter. Cone-beam Computed tomography (CBCT) images were made of the involved teeth after the intraoral periapical radiograph confirmed the size of lesion to be equal to greater than 3 mm. Three observers (endodontists) viewed the periapical, RVG and CBCT images. Upon viewing each of the images from the two imaging modalities, observers (1) measured lesion size and (2) made decisions on treatment based on each radiograph Results: No significant difference was noted in the treatment plan selected by observers using the three modalities. Post-operative radiographs did not shows any significant difference Conclusion: Lesion size and choice of treatment of periapical lesions based on CBCT radiographs do not change significantly from those made on the basis of radiographs.