Copper in the form of nanoparticles and microsized fibers was synthesized by using carbon nanotubes as a template. The size of the copper nanoparticles was controllable in the range between a few and tens of nanometers, depending on the diameter of carbon nanotubes and the preparation conditions. They could be detached from carbon nanotubes by ultrasonic treatment. Cu fibers with diameter ranging from 100 nm to several mu m were obtained when increasing the amount of Cu coated onto carbon nanotubes. which in this case became undetectable under SEM and XRD observations. The electronic structure of these two forms of Cu materials was studied by XPS and UPS and compared with that of polycrystalline Cu metal. A negative core-level binding energy shift for Cu nanoparticles and an increase in work function for Cu fibers as compared with those of the polycrystalline Cu were observed and discussed in terms of size effect.