A nanostructured sensing device based on anodic aluminum oxide (AAO) nanowells was fabricated and investigated for hydrogen gas sensing. AAO nanowells with an average pore diameter of 73 nm and with 2, 6, and 12 min anodization time were immersed in a surfactant solution and coated with an 8 nm film of palladium nanoparticles. The electrical resistance change of the nanostructured sensor with hydrogen gas exposure was used as the sensing parameter. The AAO nanowells and nanostructures were characterized using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and contact angle measurements. Using argon as a carrier gas, hydrogen concentrations as low as 0.05 vol.% (500 ppm) can be detected at room temperature. Response times as fast as 1.15 s were obtained for the AAO nanowell-Pd nanostructure detector which compared to current devices and nanostructures in development, is found to be considerably faster without compromising sensor response magnitude and selectivity. © 2008 Elsevier B.V.