Single-walled carbon nanotubes (SWNTs) produced by arc-discharge have been researched as resistive gas sensors for H2 detection. Raw as well as modified single-walled carbon nanotubes were utilised as sensor material. Two types of modification treatments were carried out on the as grown SWNT material; chemical functionalization with palladium and doping with palladium by sputtering. CNTs were deposited on alumina substrates by airbrush. Two different alumina substrates (with and without heater element) were used to obtain the sensor devices. Conductance measurements were carried out in a N2 constant flow for H2 detection. The results demonstrate that the CNTs are p-type semiconductor materials, increasing their resistance with reducing gases. SWNTs functionalized with Pd show the best response when exposed to H2 at room temperature. This work has been supported by the project NANOENER MAT2002-04630-C02-01, Good-Food. IP, IST VI FM, and the CSIC Fuel Cell Network Peer reviewed