The oxidative stripping of a saturation layer of COchem was studied on platinum nanoparticles of high shape selectivity and narrow size distribution. Nanospheres, nanocubes, and nano-octahedrons were synthesized using the water-in-oil microemulsion or polyacrylate methods. The three shapes allowed examination of the COchem stripping in relation to the geometry of the nanoparticles and presence of specific nanoscopic surface domains. Electrochemical quartz crystal nanobalance (EQCN) measurements provided evidence for the existence of more than one mechanism in the COchem stripping. This was corroborated by chronoamperometry transient for a COchem, saturation layer at stripping potentials of E-strip = 0.40, 0.50, 0.60, and 0.70 V. The first mechanism is operational in the case of COchem stripping at lower E-strip values; it proceeds without adsorption of anions or H2O molecules and corresponds to desorption of a fraction of COchem in the form of a prepeak in voltammograms or in the form of an exponential decay in chrono-amperometry (CA) transients. The second mechanism is operational in the desorption of the remaining COchem at higher E-strip values and gives rise to at least two voltammetric peaks or two CA peaks. Analysis of the experimental data and modeling of the CA transients lead to the conclusion that the stripping of a saturation layer of COchem first follows an Eley-Rideal mechanism in the early stage of the process and then a Langmuir-Hinshelwood mechanism.