Purpose: The aim of this study was to evaluate the effect of a computer-aided design/ computer-assisted manufacturing (CAD/CAM) guide on drilling the screw-access channel for lingually placed implants. Materials and Methods: Screw-channel drilling guides were fabricated on lingually placed implant models using CAD/CAM technology. The screw channels were prepared with guided or freehand drilling by 20 dental graduates. The accuracy of each screw channel was assessed for drilling entry point, channel volume, and angulation (α = .05). Results: The guided drilling group showed smaller deviations than the freehand drilling group, and prosthesis position influenced the guide effect (P .001). Conclusion: The CAD/CAM guide facilitated the screw channel preparation of cement-retained prostheses supported by lingually placed implants.