Structures and stress state of six commercial freestanding thick diamond films (> 300 mum) were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy. These films represent the typical samples synthesized by three different chemical vapor deposition (CVD) methods, including DC are, microwave plasma, and hot filament. It was found that the higher diamond deposition rate it reaches, the more non-diamond carbons it contains, and the larger the residual compressive stress it possesses. Moreover, the samples with the highest degree of optical transparency are under the lowest compressive stress. These crystal characteristics can be manipulated by selecting different deposition methods and parameters that affect nucleation rate and growth rate of diamond. The present results show that the DC are method gives poorly developed crystals, and its residual compressive stress of the films is the highest due to the fastest diamond nucleation and crystal growth rates.