This invention relates to new peptide-based compounds and their use in therapeutically effective treatments as well as for diagnostic imaging techniques. More specifically the invention relates to the use of such peptide-based compounds used as targeting vectors that bind to receptors associated with angiogenesis, in particular the αv&bgr;3 integrin receptor. Such contrast agents may thus be used for diagnosis of for example malignant diseases, heart diseases, inflammation-related diseases, rheumatoid arthritis and Kaposi's sarcoma. Moreover such compounds may also be used in therapeutic treatment of these diseases.