Novel synthetic approach for preparation of single phase porous SnO2 thin films with controllable grain size and porosity has been developed. The entire process requires neither organic solvents nor addition of any complexing agent. The thin films were deposited using the spin coating technique from an aqueous solution prepared by dissolving tin(II) oxalate in hydrogen peroxide. X-ray diffraction analysis showed that the deposited films are single-phase and their crystallite size increases as the annealing temperature is increased from 300 to 800 degrees C. It was also found that the films exhibit a preferred (110) orientation of the crystallites. Scanning electron microscopy and atomic force microscopy were employed for the estimation of thickness and surface morphological features of the films. Thickness of the films after 10 deposition cycles was about 160 nm. Roughness of the films increased with the annealing temperature increasing. It has been found from the UV-Vis spectrometry measurements that the films are highly transparent in visible spectral range. The optical band gap was determined to be in the range from 3.86 to 4.00 eV depending on the annealing temperature.