This study is concerned with deposition of neutral and charged particles in nearly developed turbulent duct flows. The cases that the duct is vertical or horizontal and when the particles carry Boltzmann, static electrification, as well as saturation charge distributions are analyzed. The mean turbulent flow field is evaluated with the aid of the FLUENT code, using the Reynolds stress transport model. Deposition rate of particles in the size range of 0.01-100 mu m are studied and the effects of electric field intensity on particle deposition velocity are evaluated. The simulation results are compared with the available experimental data, the earlier numerical results and those obtained from empirical equations for fully developed duct flows. It is shown that the electrostatic effect significantly increases the particle deposition rate.