Radiopharmaceutical chemistry has addressed the issue of biomolecular chemistry, and radiopharmaceuticals are unique in their ability to monitor receptor binding sites and enzymes. The future of diagnostic and therapeutic nuclear medicine, to study the in vivo metabolism, is focused on the use of radiolabeled protein fragments, peptide structures and DNA chains. These radiolabeled molecules represent a substantial change in the paradigms of the pharmaceutical development by employing, as a source of pharmaceuticals, capabilities of our own body, instead of considering it as a simple test-tube where strange molecules interact. Research on biomolecules complexed to radioactive metals, like Tc- 99m, Re-188, Lu-177 and Y-90, that do not alter the molecular specificity, is a topic of world interest in radiopharmaceutical investigations. Some perspectives and achievements on the preparation and analysis of main diagnostic and therapeutic radiopharmaceuticals of the third generation are presented.