The rovibronic levels of the (X) over tilde (2)A(1) and (A) over tilde B-2(2) electronic states of O-3(+) have been calculated variationally for the first time, using high-level (ICMRCI/cc-pcV5Z) ab initio diabatic potential energy surfaces which explicitly consider the non-adiabatic interaction between the two states. Vibronic levels for J=1/2, 3/2 have been calculated and assigned for energies up to 2000 cm (1) above the ground state, making comparisons with recent results from ZEKE photoelectron experiments of ozone. The procedure has good predictive capabilities and it is used to confirm previous assignments and to tentatively identify some unassigned features in the low energy part of the O-3(+) spectrum. (C) 2011 Elsevier B. V. All rights reserved.