Beta-emitting radioisotope 177 Lu has been suggested for radioimmunotherapy, peptide receptor radionuclide therapy, or another radionuclide therapy due to its excellent properties for destroying cancer cells. In this experimental investigation, natural ytterbium ( nat Yb) and enriched 176 Yb targets were irradiated with thermal neutrons at 1.2×10 14 cm -2 s -1 neutron flux for 95 hours. Using a high-purity germanium (HPGe) detector-based spectroscopy system, the post-irradiated targets were measured and the produced radioisotopes were identified according to their gamma ray emissions. Experimental results indicated that several radioisotopes such as 169 Yb and 175 Yb dominate the post-irradiated nat Yb target, though a relatively weak intensity of 177 Lu was also recorded. In contrast, 177 Lu radioisotope dominates the gamma rays observed in the post-irradiated enriched 176 Yb target following elution with HNO 3 solution. For the first time, evidence is found of 175 Yb impurity in the post-neutron-irradiated enriched 176 Yb 2 O 3 target as a result of 176 Yb(n,2n) 175 Yb nuclear reaction. This work recommends future 177 Lu radioisotope production using enriched 176 Yb 2 O 3 target.