Facial onlay augmentation is often performed as an ancillary procedure simultaneously with orthognathic surgery to improve facial appearance, with hydroxyapatite (HAp) and HAp-based composites often used as the materials of choice. The ability to apply HAp in a granular rather than solid shape form may be responsible for its comparatively reduced rate of complications. However, a known complication of HAp and HAp composites is reduction of implant volume over time associated with resorption of the material. Evaluation of the volumetric changes of implanted biphasic calcium phosphate (HAp/b-TCP)/collagen composite in the malar areas from baseline to 4 months, 9e12 months, and 18e24 months after surgery using cone beam computed tomography (CBCT) surface superimposition and volumetric subtraction was done. The average decrease of volume of implanted HAp/b-TCP 4 months after surgery was 18.6%. Further volumetric decreases were negligible and a mean total volume loss of 21.65% was found at 18e24 months postoperatively.