Diffusion profiles and effusion experiments performed on post-hydrogenated (deuterated) CVD diamond layers (grain size 2 and 0.2μm) were reported in order to study the configurations and stability of hydrogen bonding in polycrystalline undoped CVD diamond. Deuterium was used as a tracer to improve the hydrogen detection limit. The diamond layers were first annealed at 1200C in order to out-diffuse hydrogen present in the as-grown sample. Then the samples were exposed either to a radio-frequency plasma or a microwave plasma and the deuterium diffusion profiles were analyzed by secondary ion mass spectrometry. For radio-frequency and microwave plasma, the diffusion profiles were explained in term of trapping on plasma-induced defects near the surface and/or on inter- and intra-granular defects. The mean free paths of deuterium and capture radius of traps were calculated by fitting the deuterium diffusion profiles and depended on the grain sizes. Some CVD diamond layers were deposited using a gas mixture (CH4 + D2) and a deuterium concentration of 3 x 1019/cm3, originating from the vector gas, was found in these as-grown samples. The stabilities of deuterium bonding in as-grown and post-deuterated samples were compared.Hydrogen Diffusion and Stability in Polycrystalline CVD Undoped Diamond. Ballutaud, D., Jomard, F., Theys, B., Mer, C., Tromson, D., Bergonzo, P.: Diamond and Related Materials, 2001, 10[3-7], 405-10