The surface modification of polymer microspheres by complex plasma was studied. Melamine-formaldehyde spherical microparticles, falling into neon dc glow discharge, acquired an electric charge on their surface and hung in a dust trap, where the electric field strength was strong enough. They were long trapped, forming three-dimensional ordered structures. Depending on the exposure time, the particle sizes and surface properties changed. Scanning electron microscopy provided insight in the particle morphology changing. The dependence of the particle size on the exposure in plasma was measured; the modification of the surface structure was investigated. The results of the statistical processing of the surface structure are presented.