Apparent molar volumes V-2,V-phi and standard partial molar volumes V-2(0),(phi) of LiClO4, LiBr and three symmetrical tetraalkylammonium bromides R4NBr (R = ethyl, propyl, butyl) have been determined at 298.15 K from precise density measurements in solvent mixtures of ethylene carbonate with tetrahydrofuran (THF), acetonitrile (AN), ethyl acetate (EA) and dimethoxyethane (DME). It is shown that the V-2(0),phi values of LiClO4 and LiBr are dependent strongly on the nature of the solvents, whereas the contribution of CH2 group to the partial molar volume of the tetraalkylammonium salts has nothing to do with the nature of the solvents and the composition of the solvent mixtures. This provided a helpful evidence for the unsolvation of large tetraalkylammonium cations in organic solvents. The results have been discussed from ion-solvent interactions and the dielectric effect of the solvents. (C) 2004 Elsevier Ltd. All rights reserved.