149 Pm, 166 Ho, 161 Tb and 177 Lu conjugated to chemical agents (monoclonal antibodies, polypeptide, etc.) have the appropriate decay characteristics for imaging and therapeutic studies and consequently the potential to be useful in radiotherapy and diagnosis. These carrier-free radioisotopes can be produced by neutron irradiation of a lanthanide target followed by β − decay, and a posterior radiochemical separation of the daughter radionuclide from macro-amounts of the parent target. In order to produce carrier free 149 Pm, 161 Tb, 166 Ho and 177 Lu for radiotherapy, with a radionuclide purity of more than 99.9%, a device production was developed based on separation of Nd/Pm, Gb/Tb, Dy/Ho and Yb/Lu by extraction chromatography.