We investigate the interaction of single-walled carbon nanotubes (SWCNTs) and methane molecule from thefirst principles. Adsorption energies are calculated, and methane affinities for the typical semiconducting and metallicnanotubes are compared. We also discuss role of the structural defects and nanotube curvature on the adsorptioncapability of the SWCNTs. We could observe larger adsorption energies for the metallic CNTs in comparison with thesemicondueting CNTs. The obtained results for the zig zag nanotubes with various diameters reveal that the adsorptionenergy is higher for nanotubes with larger diameters. For defected tubes the adsorption energies are calculated for variousconfigurations such as methane molecule approaching to the defect sites pentagon, hexagon, and heptagon in the tubesurface. The results show that the introduce defects have an important contribution to the adsorption mechanism of themethane on SWNTs. We investigate the interaction of single-walled carbon nanotubes (SWCNTs) and methane molecule from the first principles. Adsorption energies are calculated, and methane affinities for the typical semiconducting and metallic nanotubes are compared. We also discuss role of the structural defects and nanotube curvature on the We obtained the adsorption results for the zig zag nanotubes with various leads reveal that the adsorption energy is higher for nanotubes with larger diameters. For defected tubes the adsorption energies are calculated for variousconfigurations such as methane molecule approaching to the defect sites pentagon, hexagon, and heptagon in the tubesurface. The results show that the due defects have an important contribution to the adsorption mechanism of themethane on SWNTs.