Purpose: Simultaneous insertion of multiple implants may exhibit suboptimal positions, especially in edentulous jaws considered for a fixed restoration. The aim of this study was to compare the incidence of and confounding factors in implant positioning errors related to the use of freehand and computer-aided treatment methods. Materials and Methods: A total of 353 implants were placed in 54 patients with at least one edentulous jaw using freehand and computer-aided methods involving 16 mucosa- and 12 bonesupported single- and multiple-type stereolithographic surgical guides. At the stage of prosthesis delivery, a blinded examiner evaluated seven positioning error criteria. Results were analyzed by chi-square test and logistic regression. Results: Interproximal emergence (OR = 2.82, P .0001), insufficient interimplant distance (OR = 1.42, P .0001), and improper parallelism (OR = 1.24, P = .001) errors were significantly higher in implants placed by the freehand method. The highest probability of positioning error (88%) was associated with the use of the freehand method, whereas the lowest (6%) was associated with single-type, mucosa-supported guides with other significant confounding factors. Conclusion: Utilizing computer-aided methods may alleviate the occurrence of implant positioning errors that are frequently associated with the freehand method. The use of software planning with enhanced viewing capabilities and single-type, mucosasupported stereolithographic surgical guides in suitable patients minimizes errors. Parole chiave: implant position; positioning error; malposition; guided surgery; implant prosthodontics; stereolithography