Radioimmunotherapy (RIT), an innovative approach to targeted radiation has been recognized as a potent therapeutic technique applicable to numerous cancer types. In this therapy, tumor-targeting monoclonal antibody (mAb) is employed for selective delivery of a cytotoxic radionuclide to tumor cells without binding to normal cells, thus minimizing toxicity due to nonselective exposure of the radionuclide. The RIT system generally consists of three components, a radionuclide, a targeting vector routinely, i.e. mAb, and a bifunctional ligand. The development of the adequate bifunctional ligand to effectively hold a radionuclide after being conjugated with a mAb is a critical step for enhancing the efficacy of RIT. We previously reported that the structually new chelate NETA possessing both a macrocyclic cavity and an acyclic pendant binding group binds 86Y, a PET emitting surrogate for the promising radionuclide for RIT, 90Y for the first time, with excellent kinetics, and in vitro and in vivo stability. The synthesis and evaluation of a bifunctional version of NETA, 3P-C-NETA will be described in this presentation.