Our high-level ab initio calculations show that the ZnO2+ electronic ground state of (3)Sigma symmetry is metastable with a bond length of 2.066 angstrom, an effective dissociation energy of 1.42 eV, and a double ionization energy of ZnO of 26.61 eV. Spectroscopic constants, adiabatic excitation energies, tunneling and spin-orbit induced predissociation lifetimes for the vibrational levels in the low-lying electronic states of ZnO2+ were determined and the metastability of the dication was discussed. For the lower electronic states of ZnO2+ (n = 0, 1, 2) species, the spectroscopic characteristics of the Lambda-S states were calculated and the double ionization spectrum of ZnO was simulated. (C) 2012 Elsevier B.V. All rights reserved.