Poly(diallyldimethylammonium chloride) (PDADMAC) in water and aqueous NaCl solutions was simulated by full-atomic molecular dynamics (MD). Structural characteristics (chain conformations, counterion distribution), diffusion coefficients and electrophoretic mobility were estimated from the simulations and compared with available experimental data. The preferred polycation conformation looks like a sequence of stretched fragments separated by kinks. Adding the salt to the aqueous solution makes the chains more flexible but only slightly more compact, despite significant counterion condensation. Although MD with OPLS-AA force field and SPC/E model for water somewhat overestimates the polycation mobility, the simulation reproduces rather well the experimentally observed composition dependence of the transport characteristics mediated by the polyion – counterions interaction.