The structural, electronic, and magnetic properties of Y(n)O(2) and Y(n)O(2)(-) clusters, up to n = 8, have been systematically investigated by using the density-functional approach. Our theoretical results show that the geometries of the ground-state neutral and anionic clusters are similar, except for n = 2. For the lowest-energy structures of the two systems, a two-dimensional to three-dimensional structural transition is identified. In addition, the ionization potentials, electron affinities, electron detachment energies, and gaps are carefully investigated. Here, the calculated electron affinities and electron detachment energies are in good agreement with the experimental data, implying that the predictions of the ground-state configurations of these clusters are reliable. On the basis of the optimized structures, we investigate and discuss the magnetic properties of the two systems for the first time. (PACS numbers: 75.50.Xx. 36.40.Cg,73.22.-f.).