A simple and efficient approach is developed for the synthesis of copper oxide nanorods with different morphology and crystallographic structure. Polycrystalline fine rods 10-20 nm thick and several hundred nanometers long and single crystalline thick rods 60-100 nm thick and up to 1 mum long were obtained from the reactions of copper hydrate with caustic soda solution at room temperature and 100 degreesC, respectively. The fine CuO nanorods as anode materials for Li ion battery exhibit a high electrochemical capacity of 766 mA h/g and relatively poor capacity retention as compared to thick nanorods with the single crystalline structure. The correlation between the structural features of the nanorods and their electrode performance is discussed in detail.