Titanium oxide surfaces were coated with methyl-and hydroxyl-terminated dodecyl phosphate monolayers by immersion of the substrates into aqueous solutions of the corresponding ammonium salts (DDPO4-(NH4)2 and OH-DDPO4(NH4)2). The samples were examined by contact-angle measurements and nearedge X-ray absorption fine structure spectroscopy. DDPO4 was found to form self-assembled films of comparable quality to those of the longer octadecyl phosphate prepared from an organic solvent and to those of a similar thiol/gold system. The hydroxyl-terminated adsorbates, however, established films with a much lower degree of orientation under the same preparation conditions and showed "high" water contact angle values (50-55°) for a hydrophilic surface. Mixed films of both species establish a degree of orientation between those of both pure films, which is also reflected by their wettability.