AbstractBy NMR‐Spin‐echo technique the self‐diffusion coefficients in aqueous solutions of a number of ions and of water have been measured. Measurements have been performed as a function of the concentration of the dissolved salt and of the temperature. Water (H2O) and heavy water (D2O) have been used as solvents. Only in the case of H2O, however, the self‐diffusion of the solvent has been measured. The following liquid systems have been studied in detail: LiClH2O (D Li +,DH2O); Li2SiF6H2O (D Li +,D SiF 6 −,DH2O; [(CH3)4X]2YF6D2O with X  N, P, As, Sb, and Y  Si, Ge (D(CH3)4X+,DYF6−). At various concentrations the self‐diffusion coefficients of the ions and of the water as a function of the temperature may be described by an Arrhenius law. At constant concentration in some cases two different activation energies (frequency factors resp.) occur, one for an upper, the other for a lower temperature range. The result of the measurements are discussed and partially c