In a process for preparing spherical particles of a metal oxide or hydroxide having a particle size of from 0.1 to 10 .mu.m by adding a corresponding metal alkoxide to a dispersion of water-alcohol system having dispersed therein a metal oxide or hydroxide as a seed, under alkaline conditions and allowing a decomposition product from said metal alkoxide to attach onto said seed to effect particle growth of the seed, the improvement which comprises maintaining said dispersion at a substantially constant pH within the range between 10 and 13 during the addition of the metal alkoxide to said dispersion and the subsequent particle growth of the seed, thereby to prepare mono-dispersed particles substantially free from particle aggregation having a sharp particle size distribution of a standard deviation of not greater than 0.5. The white particles so prepared may be, after separation, heat treated to provide black particles. The white or black particles may be coated with a synthetic resin in the surface. The products are useful particularly as spacers for liquid crystal display devices.