The preferential solvation of copper(II) iodate, benzoate, formate, salicylate, p-methylbenzoate, and p-nitrobenzoate has been studied in water+N-methyl-2-pyrrolidinone mixtures at 30 degrees C by Gibbs energies of transfer and solvent transport number measurements. The Gibbs transfer energies of the salts were split into their ionic values using the transfer energies of copper ion determined on the basis of the negligible liquid junction potential method. These results were also compared with those obtained on the basis of the tetraphenylarsonium tetraphenylborate method. These results have been interpreted in terms of heteroselective solvation of all the salts with the copper ion being selectively solvated by N-methyl-2-pyrrolidinone and anions by water.