There has been a ceaseless demand for lithium ion secondary batteries with higher capacities. Nano-carbons such as single wall carbon nanotubes (SWNTs) have been suggesting the potential for use as high capacity anode materials for rechargeable batteries. It is known that SWNTs show different structures and properties depending on their synthetic methods and conditions. We report on the electrochemical lithium storage properties of the SWNTs in connection with the structure in detail. Two types of SWNTs synthesized by laser-ablation and HiPco methods were used, and their lithium storage properties were compared by using cyclic voltammetry and discharge-charge measurements. The results show that these SWNTs have high reversible Li insertion capacities of ca. 730mAh/g for laser-ablation SWNTs and ca. 860mAh/g for HiPco-SWNTs, and large irreversible capacities of ca. 2500mAh/g for both SWNTs. When HiPco-SWNTs were chemically etched by ultrasonication in 5wt % H2O2 aqueous solution to reduce the length of bundles, the reversible capacity improved to ca. 1200mAh/g.