Dispersed samples of LaMnO3 prepared by the Pechini method and annealed at 500 degrees C were doped with cations of a different charge and size (Ce, Fe, Bi, Sr+Bi), while the sample surface was modified with Pt. The effects (if the doping and of the surface modification on the oxygen mobility (as estimated by O-2 TPD) in the samples and on their reactivity (as estimated by CO TPR) as related to the catalytic activity in the CO oxidation are considered.