Current analytical approximations to the solution of the Poisson-Boltzmann (PB) equation in cylindrical symmetry and in the presence of salt are compared with the corresponding numerical solution of this equation. Two new analytical solutions are presented. One has been developed from the exact analytical solution of the PB equation without salt, whereas the other has been derived as an extension of the solution of the linearized PB equation in the case of excess added salt. For all PB solutions presented the zero point of the electrostatic potential is fixed in the external solution. An analytical expression has been derived which relates the salt concentration of this reference solution to that of the rod-containing cell.