The oxygen tracer diffusion was studied in cation stoichiometric (LaMnO3 +/- delta) and A-site deficient (La0.9MnO3 +/- delta) lanthanum manganites by the isotope exchange depth profiling (IEDP) technique using SIMS depth profiling. The measured oxygen tracer diffusion coefficients were in the range of 10(-12) to 10(-15) cm(2) s(-1) and these values were comparable with the ones determined in Sr-doped lanthanum manganites. The activation energy of oxygen tracer diffusion was 240+/-23 kJ/mol in LaMnO3 +/- delta and 294 +/-11 kJ/mol in La0.9MnO3 +/- delta. A-site deficiency of up to 10% does not affect oxygen tracer diffusion in these lanthanum manganites. Evidence for fast diffusion paths assigned to grain boundary diffusion was observed in the A-site deficient material.