We derived a model descfibing the radial distribution of the ion and electron densities and the radial electric field strength in the posftive column of a glow discharge. The set of equations related to the plasma consists of the equations for particle and momentum conservation for the ions and electrons and the POISSON-equation. In a novel approach, the necessary boundary conditions in our model result from asystem of balance equations for the charge carriers on the insulated wall surrounding the positive column.