New features of ArnNa+ clusters are revealed using reliable, accurate post-Hartree--Fock computations. Molecular geometries and harmonic vibrational frequencies of ArnNa+ (n = 1-8) complexes are predicted at the MP2/6-311+G(3df) level of theory. Successive values of dissociation energy for all clusters were additionally calculated within the CCSD(T) approach. The nature of bonding in these structures is discussed based on natural population analysis and interaction energy decomposition scheme. A comprehensive discussion on the relevance of an appropriate treatment of core-valence electron correlation is provided for the ArNa+ ion. The presented data agrees well with the available experimental values. (C) 2004 Elsevier B.V. All rights reserved.