This study introduces a technique that enables fabrication of monodisperse polymer/silica hybrid particles that are useful for improving light diffusion properties. The two-step process consisting of the dispersion polymerization and sol-gel reaction was employed to produce poly(methylmethacrylate-$co$-3-(trimethoxysilyl)propyl-methacrylate) (poly(MMA-$co$-TMSPM)) hybrid particles with double bonds on their surface. After consecutive seeded emulsion polymerization, micron-sized hybrid particles with an ability to effectively adhere to optical films were fabricated. The optical thin films made of these hybrid particles with different particle sizes showed unique light diffusion behaviors; the transmittance increased as the length scale of the hybrid particles increased, while their haze remained unchanged at high values.This is because the hybrid particles with a low curvature could have less light-scattering on their surface.