This topical review briefly discusses selected highlights of research on diamond nanoparticles obtained by different methods and their potential applications in biology and medicine. In recent years nanotechnology has aroused interest of a large number of scientists who endeavor to obtain nanoparticles (which differ in size and structure of surface) using different methods, in order to determine their physical, chemical and biological properties that are in relation to the methods used in the process of their production. The knowledge developed in this way will be beneficial in an attempt to use nanoparticles more reasonably in various branches of science. The distinguishing features of carbon nanoparticles are their biocompatibility, photostability and easily chemically modified surface that results in high usefulness for intracellular studies. What is more, low toxicity of nanoparticles with many cell lines is at the center of scientific interest. This, in turn, leads to a large number of biomedical applications. The property that nanodiamonds are able to penetrate cells through endocytosis, allows delivering the drug connected with nanoparticles into cancer cells. These features of nanoparticles have given many promising leads in nanooncology, in particular in drug delivery, diagnosis, imaging, and therapy. This paper presents a summary of different classes of nanodiamond particles, the ways of their uptake into cells, an overview of the possible application of nanoparticles as nanocarriers and as a clinical theranostic platform, as well as advantages and disadvantages of using nanodiamonds in biomedicine.