The structures of monolayers of long-chain aliphatic carboxylic and phosphonic acids deposited, using Langmuir-Blodgett techniques, on metal (silver and gold), conducting glass (fluorine-doped tin oxide), and nanostructured semiconductor (titanium dioxide) substrates have been studied. In the course of these studies, the effects of pH, dissolved ions, and conditioning regime on the structure of the monolayer present at the air/water interface have been examined. Also examined have been the effects of different deposition conditions and different substrate materials on the structure of the deposited monolayer. These findings represent an extension of such studies to molecules, namely, phosphonic acids, and substrates, namely, nanostructured TiO2 films, of increasing scientific and technological importance.