Interactions between saccharides and ions in aqueous solutions are of great importance in many fi elds (chem istry, physico-chernistry, biology, food industries). Thus, this work proposes to develop a methodology dealing with the characterization and the understanding of interactions between saccharides and cations in presence of water molecules, by a quantum mechanics approach. In the fi rst part, the saccharide hydration properties (xylose, glucose, sucrose) in pure water are deterrnined. Results show that the saccharide coordination numbers, as well as the saccharides hydration enthalpy, increase with the saccharide hydrophilic group number. In the second par t, the influence of cations on saccharides hydration properties, and inversely, is evaluated. In sac charide/cation/water systems, the decrease in hydration enthalpy of cations and saccharides shows that both species are dehydrated and that saccharide dehydration depends on the nature of the cation. The dehydration sequenoe of saccharides was explained from the study of saccharide/cation interactions.