Objective: The aim of this study was to compare wide-diameter implants placed in mature bone versus implants inserted in postextraction bone. Material and Methods: A retrospective case study was made; the sample was composed of subjects who had had wide implants placed in the molar area between 2003 and 2005. Two groups were formed: implants placed in mature bone and implants in postextraction bone. A protocol was prepared in which patient age, sex, oral hygiene, implant length, type of prosthesis, and antagonist dentition were collected. After 12 months, data relating to the clinical and radiologic conditions of the implants and the success rate (criteria of Buser et al) were recorded. A statistical analysis of the variables was made (t test, Pearson correlation coefficient, analysis of variance, chi-square). Results: The study examined 162 implants placed in 100 patients. Of the 162 implants, 130 were placed in mature bone and 32 in postextraction bone. Four implants placed in mature bone failed in 4 patients (success rate of 96.9%). None of the implants placed in postextraction bone failed. Conclusions: The placement of wide-diameter implants in recent molar extraction sites has been shown to achieve similar results to implants placed in healed mature bone after 12 months of follow-up, within the limitations of this study. Keywords: immediate implants, wide-diameter implants