Relativistic calculations of the low-lying electronic states of the ZnO molecule are performed for the Lambda-Sigma states, (1)Sigma(+), (1)Pi, (1)Delta, (3)Pi and (3)Sigma , at the CCSD(T) or MRCI level, using scalar relativistic energy-consistent pseudopotentials, and the EPCISO method for spin-orbit CI coupling. The ZnO ground state is assigned to 0(+) symmetry and has (1)Sigma(+) character around the equilibrium region. The spectroscopic constants (re, omega(e)) of the 0(+) ground state are in good agreement with experimental results. Interpenetration of the vibrational levels of the two lowest 0(+) states is also shown. (C) 2008 Elsevier B. V. All rights reserved.