Hyaluronic acid fillers are widely used for the augmentation of facial soft tissues. Hyaluronic acid fillers can be monophasic or biphasic and have different characteristics, especially regarding volumetric effects and maintenance potential. However, there is paucity of long-term quantitative and objective data on clinical outcomes following hyaluronic acid injection. In this study, the authors evaluated volumetric changes over 2 years and the maintenance potentials of both types of fillers on the anteromedial cheek using objective three-dimensional measurements. This comparative split-face study enrolled participants aged 30 to 50 years who received a midfacial injection of the test filler (Belotero Volume) on one side and a random control filler (Juvéderm, Restylane SubQ, or Yvoire Contour) on the contralateral side. The authors conducted three-dimensional scanning assessments at baseline and after 30 minutes; 3 days; 2, 4, 12, and 24 weeks; and 2 years. The volume augmentation effects for the anteromedial cheek of two monophasic fillers (Belotero Volume and Juvéderm Voluma) were maintained for at least 2 years (81 percent and 66 percent, respectively, compared to the volume at 4 weeks). Two biphasic fillers (Yvoire Contour and Restylane SubQ) maintained over 50 percent volume compared to the volume 4 weeks after injection. Monophasic fillers showed better outcomes than biphasic fillers; however, both types of hyaluronic acid fillers demonstrated superior efficacy, safety, and durability for volumetric augmentation in the anteromedial cheek. Objective data obtained using three-dimensional imaging analysis will enable dermatologists to better demonstrate the results of the procedure to patients, through the provision of visual aids. Therapeutic, II.