Purpose: The purpose of this study was to compare marginal bone loss and success rates 1 year after implants had been placed in maxillary molar sites, either immediately postextraction or after the extraction sites had healed (delayed). Materials and Methods: A retrospective case study was made of subjects treated with immediate or delayed dental implants in the maxillary molar region between January 2006 and December 2008. A protocol was prepared in which patient age, sex, implant length and diameter, type of prosthesis, buccal plate width, and use of bone grafting were recorded. After 12 months, data relating to the clinical and radiologic conditions of the implants and the success rate according to the criteria of Buser et al were recorded. The variables were analyzed statistically (Student t test, Pearson correlation, Games-Howell test). Results: The study included 123 implants placed in 70 patients; 35 implants were immediate and 88 were delayed. Two immediate and six delayed implants failed, resulting in success rates of 94.3% and 93.2%, respectively. Average marginal bone loss was 0.56 mm for immediate implants and 0.67 mm for delayed implants. Conclusions: The placement of immediate implants in maxillary molar sites achieved similar results to implants placed in healed sites in the same region after 12 months. No statistically significant differences were found between implant survival rates or average marginal bone loss. Keywords: delayed implant placement, dental implants, extraction sockets, immediate dental implants, molar replacement