The controlled precipitation method allowed to the synthesis of SnO 2 with advantageous specific properties, such as size and shape employing an aqueous SnCl 2 ·2H 2 O solution as precursor. Through XRD analyses, the optimum pH value of the solution that yielded the desired product was found to be 6.25. After a thermal treatment at 600°C, the final powder presented an average particle size below 50nm with a surface area of 19m 2 g −1 and a large reactivity. The evolution of the most important functional groups during the steps involved in this synthesis route is explained in view of the results obtained with FTIR and XRD. A thorough discussion on the different intermediates involved in the whole process is presented on the basis of hydrolysis and condensation reactions. The conclusions are supported with a complete characterization through differential and gravimetric thermal analysis (DTA/TGA), electron microscopies (SEM/TEM) and surface area determinations (BET).