Oriented diamond nuclei prepared by bias‐enhanced microwave plasma chemical vapor deposition on β‐SiC and Si were characterized by x‐ray texture diffractometry. In both cases, x‐ray pole figures reveal an epitaxial relation between the orientation of diamond nuclei and the substrate. However, the angular spread of the nuclei orientation is rather large, amounting to 9°–13° (FWHM) in both polar and azimuthal directions. When growing thick diamond films on top of these already oriented diamond nuclei, the evolution of the orientational order depends critically on the growth conditions. In the case of 〈100〉 oriented nuclei, growth conditions which favor the formation of a 〈100〉 fiber texture can even improve the degree of orientational order, whereas other growth conditions result in a deterioration of the epitaxial relationship.