Purpose: Computer-aided surgery under navigation system guidance is widely applied in dental implant procedures. However, the accuracy of drilling with such navigation systems has not been comparatively evaluated alongside those of laboratory guide-based and freehand drilling. Therefore, this study aimed to compare the accuracies of these three drilling systems. Materials and Methods: A navigation system, a laboratory guide, and freehand drilling were used to drill 150 holes on 30 cast models. Two master models- one each for the maxilla and mandible-were prepared with the idea of placing five implants per cast. After drilling five holes on each cast, postoperative cone beam computed tomography images were acquired to measure the magnitude of errors. Results: The navigation system and laboratory guide were more accurate than freehand placement with respect to total errors at the entry and apex, lateral error at the apex, and angular error. The navigation system was more accurate than the laboratory guide with respect to angular error. Laboratory guide-based drilling was more accurate than freehand drilling in terms of lateral error at entry. Conclusion: In comparison with the laboratory guide and freehand placement, the navigation system exhibited lower angular and axial errors. Despite its higher accuracy, the navigation system requires the operator to pay greater attention. Keywords: computer-aided surgery, dental implant, hand drilling, laboratory guide, navigation system