Over the past decade, there has been an increased interest to filling the interior of carbon nanotubes with nanoparticles for trapping gases, magnetic control of the tubes, and catalytic applications. This study focuses on filling commercial carbon nanotubes with copper. Conventionally, suspensions or colloidal solution of nanoparticles are used for nanotube filling. In our research, we filled nanotubes with a copper salt (CuCl2) and conducted subsequent hydrogen reduction to obtain metal particles. This process helps to avoid problems with agglomeration of the metal nanoparticles in dispersion. If the metal particles in question are oxidized easily, as is the case with copper, oxides can also be reduced under hydrogen. Filling the tubes with a salt solution occurs by capillary forces. Boiling and vacuum assisted infiltration were used as two alternative filling techniques. After filling, the samples are rinsed with water to eliminate salt from the exterior of the tubes and prevent particle formation on the outer surface. SEM and TEM images show that the interior walls of carbon nanotubes are covered with a thin layer of copper chloride. XRD results confirm that copper chloride is present. After reduction under hydrogen atmosphere at 300�C for 90 min, XRD shows no copper chloride peaks and indicates presence of metallic copper.