We have carried out density-functional calculations to investigate the chemisorption of SO, SO2 and SO3 molecules on Al- and Si-doped carbon nanotubes with chiralities (5,5) and (9,0) and Al-doped graphene. Among several adsorption configurations studied, the most stable ones are those forming Al-O or Si-O bonds. SO2 adsorbs with smaller adsorption energies compared to SO and SO3. The adsorption is also accompanied by a change in the band gap energy; for the Al-doped CNT(9,0), the band gap energy drops by about 50% of its value. The adsorption energies for these gases on Al-doped graphene are comparable to those of the nanotubes. (C) 2014 Elsevier B.V. All rights reserved.