Using density functional theory and ZINDO method, the two-photon absorption (TPA) cross-sections (delta) and the second hyperpolarizabilities (gamma) of a series of stilbene derivatives with multi-branched structures have been theoretically investigated. On the basis of correct geometry and UV-VIS spectrum, the position and strength of the TPA are reported. It is found that, the multi-branched structure increases the TPA cross-section and the second hyperpolarizability in comparison to the singly branched counterpart. The delta value increases as the donor strength, the acceptor strength of the center in multi-branched structures, and the conjugation length increase. (C) 2002 Elsevier Science B.V. All rights reserved.