A low-cost and environmentally friendly hydrothermal route to the synthesis of hierarchical SnO₂nanostructures was described. The structure and morphology of the as-prepared product were characterized by various characterization techniques. The results revealed that these nanostructures were built from two-dimensional (2 D) nanosheets with the thicknesses of about 8 nm. Moreover, the amount of hydrochloric acid played a crucial role in the control of the final size and morphology of product. Gas sensors based on hierarchical SnO₂nanostructures were fabricated, and their gas sensing properties were tested for response to ethanol, acetone, formaldehyde, CO, toluene, H-2 and H2S gases. The sensor showed excellent selectivity toward ethanol. At an ethanol concentration of 100 ppm, the response of the hierarchical SnO₂nanosheets was about 33, which was about 2.5 times higher than that of the nanoparticles. The response time of the sensor to 60 ppm ethanol was shorter than 11 s at the optimal operating temperature of 275℃. The enhancement in gas sensing properties was attributed to their unique structure.