The effects of the crystallographic orientation on the H 2 gas sensing properties were investigated in highly oriented polycrystalline Pd-doped SnO 2 films, which were obtained using rf magnetron sputtering of a Pd (0.5wt%)-SnO 2 target on various substrates (a-, m-, r-, and c-cut sapphire and quartz). All the films had a similar thickness (∼110nm), root-mean-square (rms) roughness (∼1.3nm), surface area, and chemical status (O, Sn, and Pd). However, the orientation of the films was strongly affected by the orientation of the substrates. The (101), (002), and (101) oriented films were grown on (1 1 2¯ 0) (a-cut), (1 0 1¯ 0) (m-cut), and (1 1¯ 0 2) (r-cut) Al 2 O 3 substrates, respectively, and rather randomly oriented films were deposited on (0001) (c-cut) Al 2 O 3 and quartz substrates. In addition, the oriented Pd-doped SnO 2 films were highly textured and had in-plane orientation relationships with the substrates similar to the epitaxial films. The (101) Pd-doped SnO 2 films on (1 1 2¯ 0) and (1 1¯ 0 2) Al 2 O 3 showed a considerably higher H 2 sensitivity, and their gas response decreased with increasing sensing temperature (400–550°C). The films deposited on (1 0 1¯ 0) and (0001) Al 2 O 3 showed the maximum sensitivity at 500°C. The comparison of the H 2 gas response between undoped and Pd-doped SnO 2 films revealed that the Pd-doping shifted the optimum sensing temperature to a lower value instead of improving the gas sensitivity.