We apply a lattice-based self-consistent mean field theory in order to investigate poly-disperse polymer brushes dissolved in good solvent. The systems investigated consist of asymmetric poly(dimethylsiloxane)-polystyrene di-block copolymers near air-ethylbenzoate interface and of diblock copolymer polystyrene-poly(ethyl oxide) deposited on a air-water interface. Our results have been compared to experimental data from neutron reflectivity experiments and have shown very good agreement. We have also systematically studied the structure of the bi-disperse and tri-disperse brush for various values of the molar fraction of the chains and of the overall surface densities. In addition, we have investigated the behavior of the brushes in other type of solvents. (c) 2005 Elsevier Ltd. All rights reserved.