The need of new biocompatible materials with superior properties and flexibility in their surface termination and functionalization for medical applications is constantly increasing. Due to the combination of intrinsic properties, chemically deposited diamond thin films are proposed as one of the most promising material in this field. They are chemically/ mechanically/physically stable and their surface can be modified by a variety of chemical or plasmatic techniques. In the present work, different diamond nano-structures, i.e. nano-rods, ultra nano-cones and nano-cones, were prepared by plasma etching process by applying various masking materials (Ni, Au and diamond powder). The impact of these diamond nanostructures on the growth of human osteoblasts was investigated by fluorescence microscopy. We observed that adhesion of osteoblasts varied, depending upon the diamond nano-structure as visualized, 1 or 48 h after seeding. Many but very fine focal adhesions are formed on nano-rods; however, few but large ones are formed on ultra nano-cones and nano-cones. The cell adhesion was controlled by the nano-structuring, thereupon their usage in bio-medical applications is considered.