Abstract: Diamond films grown on titanium substrates by hot filament chemical vapour deposition (HF-CVD) were characterised by X-ray diffraction (XRD) measurements using both synchrotron radiation (SR) and a Cu X-ray tube. Grazing incidence diffraction (GID) measurements pointed out the presence of different phases at the film-substrate interface, i.e. titanium hydride (TiH2) and titanium carbide (TiC). The experimental data allowed us to determine, by means of a libe broadening analysis (LBA), the crystallographic features and microstrain of the diamond layer and of the other phases.