Quantum chemical analyses of poly(p-phenylenevinylene) (PPV)-based polymers with conformational and chemical defects are presented. It is shown that defects leading to tetrahedral kinks in the polymerization direction that were proposed previously to explain the optical anisotropy of polymer films (Hu et al. Nature 2000, 405, 1030) are indeed energetically stable. These defects are shown not to affect the primary electronic absorption band, but they may localize the electron-hole excitation in one segment of the polymer chain.1052661036107