Time dependent density functional theory has been applied to analyze the effect of substituent groups on one-photon (OPA) and two-photon (TPA) absorption properties of extended amine-terminated phenylenevinylene oligomers. All investigated molecules are characterized by increased TPA activity. Calculated TPA cross-sections for these compounds do not show TPA enhancements observed in experimental measurements. Stabilization of the TPA active excited state in these chromophores leads to the small (∼0.2eV) energy separation between the OPA and TPA allowed excited states, which agrees well with experimental data and may lead to the enhancement of the TPA response due to the strong vibronic couplings.