AbstrAct Purpose: Nanostructured carbon nanomaterials (e.g., nanocrystalline diamond films and particles, carbon nanotubes, carbon onions, fullerenes, etc.) are being extensively explored for numerous biomedical applications in surgical implants, therapy, drug delivery, and biosensoring due to their interesting physical, chemical, and biological properties. Such applications of carbon nanomaterials often require specific surface functionality to be introduced for better integration of these materials with physiological environment. In the last decade, substantial progress has been made in the development of controllable surface modification methods and in the introduction of different functional groups on the surface of carbon nanomaterials. Design/methodology/approach: This paper briefly overviews the surface modification and functionalization approaches for various carbon nanomaterials, and it focuses on the plasma modification and functionalization of nanocrystalline diamond films, diamond nanoparticles, and carbon nanospheres. The results on the surface characterization using FTIR and XPS techniques, and the preliminary studies of cellular response to these modified carbon nanomaterials are presented and discussed.