SnO2 nanoparticles are of interest for gas sensor applications because the surface area is much larger compared to conventional powders. Thus, interactions between the material and the gases, which occur on the surface sites of the particles, are increased considerably. The preparation of SnO2 powders has been investigated following two forced precipitation systems: the hydrolysis reaction of SnC14 in an emulsion media and the hydrolysis reaction of Sn2+ in the presence of a complexing ligand (CH3COO−). Spherical nanoparticles in the 10 to 100 nm range and with a narrow size distribution were synthesized by both precipitating routes. In both cases, it has been demonstrated that the most important parameter which controlled the particle size was the nature of the associated anion. When this associated anion or ligand is able to form a strong complex with the colloidal subunits, a barrier against Van der Waals attraction is created which results in little growth. This greatly influences the agglomeration/growth kinetics during the precipitation. The effect of acetate chelating ligands which resulted in the SnO2 nano-powders formed of 5–10 nm crystallites will be presented and discussed. Preliminary results on the gas (N2, NO) adsorption studies on pellets formed from these powders are also presented.