The selectivity of chemical vapor deposition copper for metal or metallic substrates in preference to silicon dioxide was investigated systematically using copper (II) hexafluoroacetylacetonate, Cu(HFA)(2), with pure hydrogen or hydrogen/argon mixtures (1:3) in a cold wall type vertical flow reactor as a function of measured total pressure (2-10 Ton), deposition temperature (310-390 degrees C), and inlet precursor mole fraction (0.008-0.09). The deposition temperature was found to be the most important parameter. Temperatures of 310-360 degrees C resulted in selective deposition under the above conditions. Auger electron spectroscopy depth profiles indicate the composition of the films. Some local nucleation of copper due to the surface imperfections on silicon oxide was observed. These studies help to clarify some discordant results reported in the literature by determining to a good approximation the conditions of temperature, pressure and gas phase composition under which selective deposition of copper was observed.