The one- and two-photon absorption properties of 2,5-bis[4-(2-arylvinyl)phenyl]-1,3,4-oxadiazoles are investigated using response theory at DFT level. It is found that both one- and two-photon absorption properties are extremely sensitive to the geometry of the molecules, and the two-photon absorption cross section is dramatically reduced by the geometrical conformation distortion. The HF geometry is shown to be more realistic. The p enters in the compounds play different roles closely related with their different optical performances. The strongest two-photon performances for the compounds are predicted at suitable excited wavelengths. The maximum one- photon absorption is found to be non-monotonously dependent on the electron-donating ability of the terminal groups. (C) 2008 Published by Elsevier B. V.