Mono and polycrystalline Chemical Vapor Deposited (CVD) diamond is a promising material for several advanced topics: microchips substrate, biological applications, UV and particle detection. Commercial CVD diamonds are available in small square size, commonly 3-5 millimeters side and 0.5-1.5 millimeters thickness. To improve diamond reliability for described applications, it is important to have a quality control on diamond samples, not only for electrical constants but also for optical characteristics and surface roughness. In this paper we present an optical characterization method based on interferometric instruments, to measure surface structure and internal homogeneity of mono ad polycrystalline commercial CVD diamonds, with measurement examples.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.