[en] The effects of scanned 2 MeV He⁺ and 1.4 MeV H⁺ microbeam irradiation on unimplanted and P implanted diamond are discussed. Although diamond was found to be resistant to lattice defect production, it was found to swell very rapidly in comparison with other materials, giving rise to serious swelling induced dechanneling at scan edges at relatively low doses (10¹⁷/cm² for 2 MeV He⁺). Microbeams annealed the damage due to a 1.5 μm deep Phosphorus implantation at a dose of 10¹⁵P⁺/cm². The implantation damage was reduced at a dose of (1.6 x 10¹⁷/cm²) by up to 21 % for 2 MeV He⁺ irradiation, up to 16% for high flux 1.4 MeV H⁺ irradiation and 12% for low flux H⁺ irradiation. For the choice of analysis beam, all these beam effects were found to be most significant for He⁺ microbeams, so H⁺ microbeams should be used for analysis of diamond unless high depth resolution is required. 13 refs., 10 figs