The dipole moment, static linear polarizability and first hyperpolarizability of donor-acceptor azo-enaminone isomers have been calculated with both Hartree-Fock (HF) method and second-order Moller-Plesset perturbation theory (MP2), using the 6-31G and 6-31G+p basis sets. Two structural isomers of substituted azo-enaminones have been studied to point out the first hyperpolarizability geometry-dependencies associated to the type of isomerization. Our results show that the relative orientation of donor groups in chromophores has an important impact on the magnitude of the first hyperpolarizability. (c) 2005 Elsevier B.V. All rights reserved.