Abstract: The density functional theory(DFT)is used for the description of adsorption of methane on single walled carbon nanotubes(SWNT). Methane molecule is modeled by the Lennard-Jones potential,while the interaction between wall- fluid molecules is represented by the potential function proposed by Tjatjopoulos et al. To verify the DFT method, a comparison of the local density profiles and adsorption isotherms from the DFT and computer simulation for the tube diameter of 4.077 nm at 300 K is presented. Furthermore, adsorption isotherms for the SWNT of diameter 1.632 , 2.04 ,3.805 and 4.077 nm at 148 K are given in this short communication as a preliminary report.