O-18-enriched SiO2 thin film with the O-16:O-18 ratio of around 1:1 has been analyzed by laser-assisted atom probe tomography (LA-APT) using 343 nm-wavelength ultraviolet laser or 532 nm-wavelength green laser in order to investigate the quantitativeness of the oxygen concentration determined by LA-APT. No clear evidence for detecting (OO++)-O-16-O-18 signals was found in mass spectra, implying that the peaks at mass/charge of 16 and 18 are dominated by O+, not by O-2(++). The calculated elemental composition indicated significant loss of oxygen in LA-APT analysis of SiO2. (C) 2013 Elsevier B. V. All rights reserved.