Background: Diagnosis of external root resorption (ERR) cavities may be challenging, especially when no clinical signs are seen. Therefore, the aim of this study was to compare the efficacy of conventional intraoral film radiography, charge-coupled device (CCD) detector, photostimulable phosphor plate (PSP) detector, and cone beam computed tomography (CBCT) for the detection of ERR. Methods: The study sample comprised 54 maxillary first premolars. Cavities were created by using a low-speed handpiece with round diamond burs of 1 mm in diameter. Digital and conventional radiographs were taken from each tooth. Three observers examined all images for the presence of resorption cavities. Data were statistically analyzed with the χ2 test. The reliability and degrees of agreement were also determined by the mean of Cohen's Kappa analysis. Results: The differences between the imaging methods in correct detection of root resorption for all sizes were not significant. For locations of root resorption, significant differences were found between CBCT and other methods in the apical regions. Conclusions: CBCT was only useful for detection of cavities located in the apical one-third of the root, compared to other digital or conventional methods.