Molecular and dissociative adsorption of O2 on Au atoms supported on the regular and defected hexagonal boron nitride (h-BN) surface has been studied theoretically using density functional theory. It is shown that even weak interaction of Au with the defect-free h-BN support has an unusually strong influence on the binding and catalytic activation of the molecular oxygen. The strong interaction of Au with vacancy point defects on the h-BN surface is accompanied by the large charge transfer to/from the adsorbate which can considerably affect the catalytic activity of the supported Au. It is demonstrated that activation of the molecular O2 and barriers for O2 dissociation on the supported Au atom can be affected by the interaction of Au with the pristine or defected h-BN support. Therefore, the h-BN surface cannot be considered as an absolutely inert support for Au. © 2012 Wiley Periodicals, Inc.