Purpose: To compare the 3-year outcome of dental implants placed simultaneously or delayed with intraoral onlay block bone grafts. Materials and Methods: A retrospective study was conducted of patients subjected to localized lateral alveolar ridge augmentation with intraoral onlay autogenous block bone grafts before or at implant placement between 2005 and 2010 in the Oral Surgery Unit of the University of Valencia (Valencia, Spain). The parameters evaluated at follow-up visits were implant survival and success rates, peri-implant soft tissue conditions (Plaque Index and Bleeding Index, probing depth, width of keratinized mucosa, and facial mucosal retraction), radiographic peri-implant marginal bone loss, and patient satisfaction. Results: Thirtyfour patients with 53 implants (23 delayed and 30 simultaneous) were included. After 3 years of loading, the cumulative implant success rate was 83.3% for simultaneous and 96.9% for delayed implants (P = .217). Average marginal bone loss was 1.15 ± 1.67 mm for simultaneously inserted implants and 0.29 ± 0.35 mm for delayed implants (P .01). There were no significant differences in Plaque Index or modified Bleeding Index between the groups. Peri-implant facial mucosal recession was more frequent in the simultaneous implant group (26.6% vs 13%), though the difference was not statistically significant. General patient satisfaction averaged 9.05 ± 0.82, and good quality of life was reported by all patients. Conclusion: Despite its sample size and design limitations, the delayed procedure showed less marginal bone loss and a lower prevalence of facial mucosal recession than the simultaneous implant placement procedure at 3 years postloading. Keywords: alveolar ridge augmentation, bone grafting, dental implants