The electronic structure of NaCl-w(n) (w equivalent to H2O and n = 1-6, 8) clusters was investigated by ab initio and time dependent density functional theory calculations. Upon photoexcitation, when n<5 the electronic density migrates from one of the Cl valence p orbitals to the Na atom. When ngreater than or equal to5, the electronic density associated with one of these orbitals delocalizes over the nearby water molecules indicating the formation of CTTS states in the clusters. When ngreater than or equal to6, contact ion-pair (CIP) and solvent separated ion-pair (SSIP) structures are found. The onset of charge separation in the ground state of small NaCl-water clusters seems to coincide with the formation of CTTS states upon photoexcitation. (C) 2004 Elsevier B.V. All rights reserved.