Nanosystems have unique physical and biological properties. Various systems have been designed for medical use and offer promising ways of delivering drugs at high concentrations at sites of interest, e.g., cancer lesions, while reducing systemic side effects. Nanotechnology has also opened ways for the development of contrast agents and radiopharmaceuticals for specific targeting, which is presently changing research strategies in the field of magnetic resonance imaging, ultrasound imaging and nuclear medicine applications. This article aims to overview how "nanomedicine" is presently influencing drug design for diagnostic and therapeutic purposes.