This work is devoted to the elucidation the applicability of jellium model to the description ofalkali cluster properties on the basis of comparison the jellium model results with those derived from experiment and within ab initio theoretical framework. On the basis of the Hartree-Fock and local-density approximation deformed jellium model we have calculated the binding energies per atom, ionization potentials, deformation parameters and the optimized values of the Wigner-Seitz radii for neutral and singly charged sodium clusters with the number of atoms N≤20. These characteristics are compared with the results derived from the ab initio all-electron simulations of cluster electronic and ionic structure based on the density functional theory as well as on the post Hartree-Fock perturbation theory on many-electron correlation interaction. The comparison performed demonstrates the great role of cluster shape deformations in the formation cluster properties and the quite reasonable level of applicability of the deformed jellium model.