BACKGROUND The nonablative 1,550-nm erbium-doped fractional photothermolysis system (FPS) has been effectively used for scar treatments, but it seems that several sessions of treatment must be delivered to achieve satisfactory improvement. OBJECTIVES To evaluate the efficacy and safety of the combined use of two treatment modes of an ablative 10,600-nm carbon dioxide fractional laser system (CO2 FS) on acne scars. METHODS Twenty Korean patients with atrophic acne scars treated with a single session of Ultrapulse Encore laser (Lumenis Inc., Santa Clara, CA) were enrolled. The laser fluences were delivered to the scars using the Deep FX mode. Additional treatment using the Active FX mode was performed throughout the entire face. RESULTS Follow-up results revealed that one patient had clinical improvement of 76% to 100%, nine had improvements of 51% to 75%, seven had moderate improvements of 26% to 50%, and three had minimal to no improvements. The mean duration of post-therapy crusting or scaling was 6.3±3.0 days, and post-therapy erythema lasted 2.8±4.6 days. CONCLUSION We suggest that CO2 FS used with a combination of two different treatment modes may provide a new treatment algorithm for acne scars in Asians.