AbstractResveratrol, a natural product derived from grapes, is a phytoalexin with antioxidative activity. In this work we present initial results of an ongoing study of the geometry of the ground state and of the first two (singlet and triplet) excited states of resveratrol and the structurally related compounds diethyl‐stilbestrol‐stilbene and trans‐stilbene. The molecular geometries were optimized both at the semiempirical and ab initio (restricted Hartree–Fock/6‐31G*) levels, and the corresponding absorption spectra were calculated using the intermediate neglect of differential overlap/ spectroscopically parameterized with interaction of configurations (INDO/S‐CI) methodology. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 95: 213–218, 2003