Two novel bifunctional chelating agents (BFCAs) based on the structure of 10-(2-hydroxypropyl)-1,4,7-tetraazacyclododecane-1,4,7-triacetic acid (HP-DO3A) have been designed and synthesized. BFCAs are able to strongly coordinate metals (e.g.Gd(III)) and radiometals (e.g.⁹⁰Y(III), ¹⁷⁷Lu(III) and ¹¹¹In(III)), and find applications in the synthesis of products for the imaging and treatment of several cancer types. Indeed, these two BFCAs have been employed in solid-phase peptide synthesis (SPPS) and coupled to well-known peptides such as bombesin and RGD analogues in order to target tumor cells. We also report here the conjugation of one of them to Lys⁸-oxytocin and radiolabeling with ¹¹¹In(III) to obtain a new radiopharmaceutical product with potential applications in the diagnosis of tumors over-expressing oxytocin receptors.