To provide a dispersion of hollow SiO 2 , capable of obtaining, when formed into a coating composition, an antireflection film having high antireflection properties and low chroma saturation by forming a low refractive index coating film having a refractive index gradient. A dispersion of fine silica particles, having agglomerated particles which are agglomerates of primary fine particles of hollow SiO 2 dispersed in a dispersion medium, wherein the average particle size of the agglomerated particles is within a range of from 60 to 400 nm, and the average particle size is at least 1.5 times the average primary particle size of the silica. When a coating composition containing the dispersion is to be obtained, the matrix component is preferably a precursor of a metal oxide or an organic resin. By applying the coating composition to a substrate, a substrate with an antireflection coating film is obtained.