We report the facile synthesis of thin-walled SnO2 nanotubes (NTs) with numerous clustered pores (pore radius 6.56 nm) and high surface area (125.63 m(2)/g) via selective etching of core (SiO2) region in SiO2-SnO2 composite nanofibers (NFs), in which SnO2 phase preferentially occupies the shell while SiO2 is concentrated in the center of the composite NFs. The SiO2-etched SnO2 NTs are composed of ultrasmall crystallites (similar to 6 nm in size) originating from crystal growth inhibition by small SiO2 domains, which are partially segregated in the polycrystalline SnO2 shell during calcination. These features account for efficacious diffusion and innumerable active sites, which maximize interaction between background gas (air) and analyte gas (H2S). Evaluation of gas-sensing performance of the porous SnO2 NTs before and after decorating the exterior and interior walls with Pt nanoparticles (NPs) reveals exceptional selectivity and superior response (R-a/R-g) of 154.8 and 89.3 to 5 and 1 ppm of H2S, respectively. Excellent gas-sensing characteristics are attributed to the porous topography, nanosized crystallites, high surface area, and the catalytic activity of Pt/PtOx NPs.