The hierarchical undoped and Cd-doped SnO₂nanostructures had been synthesized via a low-cost and environmentally friendly hydrothermal route. The morphology and structure of the as-prepared product were characterized by X-ray diffraction (XRD), field-emission electron microscopy (FESEM), and transmission electron microscopy (TEM). The images of field-emission electron microscopy and transmission electron microscopy showed that pure and Cd-doped SnO₂hierarchical architectures were built from one-dimensional nanorods. X-ray diffraction (XRD) of the doped samples revealed that Cd incorporation led to lattice deformation without destroying the original crystal structure. Gas sensors based on undoped and Cd-doped SnO₂nanorods were fabricated, and their gas sensing properties were tested for various gases. The 3.0 wt% Cd-doped SnO₂based sensor showed excellent selectivity toward H₂S at the operating temperature 275℃, giving a response of about 31-10 ppm, which was about 22 times higher than that of sensor based on pure SnO₂.