Nanodiamond particles (NDs) are unique among different nanomaterials due to their specific features and benefits. ND, also known as ultra-dispersed diamond or ultra nanocrystalline diamond, is a member of a diverse family of nanocarbons that includes fullerenes, nanotubes, graphene, amorphous dense and porous networks. Unique characteristics combined with a moderate production cost and commercial availability favorably distinguish NDs from many other nanoparticles, which have been tried as fillers in polymer nanocomposites. Main advantages of ND particles for nanocomposites stem from unique properties, such as diamond structure that provides superior Young's modulus, hardness, high thermal conductivity and electrical resistivity, low coefficient of friction, chemical stability, and biocompatibility.