Purpose: To compare the accuracy of digital and conventional impression techniques for partially and completely edentulous patients and to determine the effect of different variables on the accuracy outcomes. Materials and Methods: An electronic and manual search was conducted to identify studies reporting on the accuracy of implant impressions. Pooled data were descriptively analyzed. Factors affecting the accuracy were identified, and their impact on accuracy outcomes was assessed. Results: The 76 studies that fulfilled the inclusion criteria featured 4 clinical studies and 72 in vitro studies. Studies were grouped according to edentulism; 41 reported on completely edentulous and 35 on partially edentulous patients. For completely edentulous patients, most in vitro studies and all three clinical studies demonstrated better accuracy with the splinted vs the nonsplinted technique (15 studies, splint; 1, nonsplint; 9, no difference). One clinical study and half of the in vitro studies reported better accuracy with the open-tray vs the closed-tray technique (10 studies, open-tray; 1, closed-tray; 10, no difference). For partially edentulous patients, one clinical study and most in vitro studies showed better accuracy with the splinted vs the nonsplinted technique (8 studies, splint; 2, nonsplint; 3, no difference). The majority of in vitro studies showed better accuracy with the open-tray vs the closed-tray technique (10 studies, open-tray; 1, closed-tray; 7, no difference), but the only clinical study reported no difference. Conclusion: The splinted impression technique is more accurate for both partially and completely edentulous patients. The open-tray technique is more accurate than the closed-tray for completely edentulous patients, but for partially edentulous patients there seems to be no difference. The impression material (polyether or polyvinylsiloxane) has no effect on the accuracy. The implant angulation affects the accuracy of implant impressions, while there are insufficient studies for the effect of implant connection type. Further accuracy studies are needed regarding digital implant impressions. Keywords: accuracy, dental implants, digital impressions, edentulous, implant impressions, impression techniques