Compound fine particles include inorganic fine particles and an organic polymer bound to surfaces of the inorganic fine particles, and have an average particle diameter of 5 to 200 nm and a particle diameter variation coefficient of 50% or less. The compound fine particles are obtainable by hydrolyzing and condensing an organic polymer, wherein the organic polymer has, per molecule, at least one polysiloxane group containing at least one Si--OR.sup.1 group, wherein R.sup.1 denotes a hydrogen atom, an unsubstituted or substituted alkyl group, or an unsubstituted or substituted acyl group. A compound fine particle dispersion includes the compound fine particles and a dispersion medium. A composition for forming a film includes this dispersion.