We investigate the equivalence between the Boltzmann (or field) approach and the particle approach for the definition of the diffusion coefficient in the presence of electron-electron collisions. Accordingly, we introduce a ‘‘model’’ collision operator as well as a ‘‘model’’ electron distribution function which can be used in a one-particle numerical procedure. In this way one can overcome the difficulties connected with the calculation of the diffusion coefficient in the presence of electron-electron collisions within the framework of the particle approach.