The local structure around the oxide ions in LnO(1.5)-CeO2 (Ln = La, Nd) was studied by using (ONMR)-O-17 spectroscopy. Each spectrum of LnO(1.5)-CeO2 showed a broad peak due to a distribution of oxygen tetrahedra. From the peak separation, the relative numbers of oxygen tetrahedra, O[Ce](4), O[Ce](3)[Ln], and O[Ce](2)[Ln](2), were determined quantitatively. In the La2O3-CeO2 system, the amounts of O[Ce](4), O[Ce](3)[Ln], and O[Ce](2)[Ln](2) deviated from the calculated value for over 20 mol % La-doped ceria (LDC). The distribution of oxygen tetrahedra for LnO(1.5)-CeO2 differed from those in LnO(1.5)-CeO2 (Ln = Nd, Y). These results suggest that the stability of the oxygen tetrahedra changes with the size of the doped ions.