Thin films of mixed-conducting hydrous ruthenium dioxide (RuO2 (.) xH(2)O or RuOxHy) were deposited via chemical vapor deposition at ambient pressure and temperature. The RuO4(g) precursor was generated in situ and reduced to RuO2 (.) xH(2)O when it contacted specific functional groups, including alcohols, thiols, amines/amides, and clean metal surfaces. The RuO4 was nonreactive when in contacted with surfaces of hydrocarbons, carboxylic acid groups, or metal oxides. Because of the selectivity of the deposition process, RuO2 (.) xH(2)O lines and patterns can be formed on substrates that are decorated with specific areas of reactive and nonreactive functional groups. RuO2 (.) xH(2)O films are conductive, catalytic for chloride evolution from brine, and may ultimately be useful as oxidation catalysts and methanol barrier layers in direct methanol fuel cells. (c) 2005 The Electrochemical Society. All rights reserved.