Isotope exchange of oxygen 18O2 with the boundary of nanograins of oxide LaMnO3+δ obtained by the method of shock-wave loading was investigated in the temperature range of 400 - 500°C. It was established that the temperature dependence of the isotope exchange rate is described by the Arrhenius expression, the activation energy and the pre-exponential factor being 1.67 eV and 1.8°102 cm/s, respectively. Comparison with literature data has shown that for oxide LaMnO3+δ, a significant difference in activation energies and pre-exponential factors is observed for the isotope exchange rate with a 'defect-free' surface and the nanograin boundary. In case of the boundary, these parameters were higher: the activation energy about two times, and the pre-exponential factor, by almost 7 orders of magnitude. © (2010) Trans Tech Publications.