Abstract: The present invention relates to novel hybrid cyclopeptide compounds embodying pyrrolidine- or piperidine-based amino acid substructures grafted onto a RGD (-Arg-Gly-Asp-) tripeptide sequence and acting as targeting ligands towards integrin receptors, intended, for example, for the treatment of altered angiogenic phenomena or for the preparation of therapeutically and/or diagnostically useful compounds; the invention also concerns a process for the synthesis of said cyclopeptides and biologically active derivatives thereof.