Purpose: The aim of this study was to analyze the reliability of cone beam computed tomography (CBCT) in assessing the grayscale density (GSD) of bone by comparing it with microcomputed tomography (μ-CT) data. Materials and Methods: A total of 50 subjects with lost mandibular molars were included in the study. To assess the bone GSD, a previously fabricated template made of acrylic resin with a 2-mm-diameter metal rod was positioned, and CBCT was performed. The bone biopsies for μ-CT analysis were then obtained during implant surgery. The relationship between GSD assessed by CBCT and data from μ-CT analysis was studied using Spearman's rank correlation. Results: A total of 38 biopsies were available for μ-CT analysis. Positive correlations were identified between GSD and bone volumetric fraction (BV/TV) (r = 0.835, P .001), bone volume (BV) (r = 0.353, P = .030), trabecular spacing (Tb.Sp) (r = -0.535, P = .001), and mean total volume (TV) (r = 0.470, P = .003). There was a clear positive linear correlation between normal values of GSD ( 700) and BV (r = 0.545). Conclusion: This study demonstrated the correlation between GSD assessed by CBCT and bone density assessed by μ-CT in the posterior mandible. For areas of typical bone density, there seems to be a positive linear correlation between GSD assessed by CBCT and bone density assessed by μ-CT. Keywords: alveolar bone, complication, cone beam computed tomography, dental implant, diagnostic imaging, endosseous implant