Nanomedicine can be defined as the application of nanotechnology to the prevention and treatment of diseases as well as for diagnosis purposes. In this context, the development of various types of drug-carrier nanodevices offers new strategies for targeted drug delivery, minimising the secondary effects and the toxicity associated to drug widespread to healthy organs or cells. This review is divided in two different parts. The first one summarizes the main types of nanomedicines developed in the past few decades, including drug nanocrystals, polymer therapeutics, lipid-nanosized and polymeric-nanosized drug delivery systems. The second part of our review is devoted, more specifically, to the presentation of polymeric nanoparticles. Here, we discuss various aspects of nanoparticle formulation, characterization, behaviour in the body and some of their potential applications. More particularly we present some approaches for the treatment of cancer, treatment of infectious diseases and the potential of these nanoparticles as adjuvants for vaccination purposes.