The SnO2 (from Sn dissolved in HNO3, 8.8 m(2)/g, or precipitated from SnCl, *5H(2)O with NHOH, 10.2 m(2)/g) dried 2 hl 100degreesC and calcined 4 h/600degreesC, was (i) impregnated with 0.5-2.5% Pt from H2PtCl6, or (ii) electrosprayed with Pt atoms knocked out from a Pt cathode with Ar ions (novel prepn. method). Catalyst (0.21 g, compressed) activities were intercompared in the T-programmed surface oxidation of CO in a CO(500 ppm)-air mixture, 40 mL/min, over 40-550degreesC (ramp rate, 20degreesC/min) and expressed as the lowest temperatures (T) at which 90% CO converted into CO2. With 1%Pt (Pt dispersion degree, 48.701.), the catalyst was more active than Pt black. The catalyst (ii) was the least active, sorbed no H-2, yet after due modifications the technique seems promising. The SnO2 sp. surface was minor factor; Pt dispersion degree was decisive.