The Er:YAG laser, with or without phosphoric acid, is used to promote enamel surface changes to increase restorative material retention. However, such irradiation might induce subsurface enamel damage. In the present study, X-ray microtomography was used to compare the subsurface enamel beneath laser and acid conditioned; laser-only etched and acid-only etched surfaces. Laser and acid conditioning increased the etching depth, but did not induce significant damage in the enamel subsurface. Analysis of the laser-only etched enamel subsurface revealed a small reduction in mineral concentration suggesting an increase in porosity, allowing greater penetration of acid and resulting in an increased acid-etch depth.