Using first-principle calculations employing density functional theory (DFT) the stability of a (3; 3) carbon nanotube (CNT) intercalated with lithium atoms, with respect to their position as well as Li/C ratio, is studied. On varying the distance of a lithium atom from the axis of the CNT in the radial direction, through the center of a graphitic hexagon, minimum of energy of the system occurs at a distance of 3.8 Å from the axis. Keeping the distance of the lithium atom from the tube axis fixed at 3.8 Å, intercalation energy (ΔE) was calculated while the number of lithium atoms is varied from one (Li1C12, -0:511 eV) to six (Li6C12, -0:615 eV). It is found that the intercalation becomes more favorable with the increase in number of lithium atoms intercalated and increase in the symmetry of the intercalated system. The maximum intercalation energy difference between successive lithium atom additions lay within 0.1 eV. © (2013) Trans Tech Publications, Switzerland.