Results on the structure, composition and properties of diamond films deposited onto WC-Co cemented carbides via special multilayer barrier interlayers preliminary seeded by nano-grained diamond particles are presented. The barrier interlayers comprise a layer adjacent to the substrate, which completely prevents substrate decarburization and Co diffusion from the substrate, and a diamond-bonding layer needed to obtain an enhanced adhesion of the PACVD diamond coating. Preliminary seeding the barrier interlayers with nano-grain diamond particles by use of a laser ablation technique allows a fine-grained, uniform and highly adherent diamond coating of high quality to be deposited by use of a conventional PACVD technique. Results on the nature of the interaction between the diamond nano-grained seeds and barrier interlayer are also presented.