1:1 CT complexes formed between some crown polythioethers and π-electron acceptors (DDQ, TCNE and CHL) have been synthesized and characterized. Spectral characteristics and formation constants of the CT complexes have been measured at 25°C. The effects of donor molecular structure, π-acceptor electron affinity and solvent polarity on the stabilities of these CT complexes have been investigated and discussed. It is deduced that such complexes are of weak n-π type where the ground state wave function is described primarily by the nonbonding structure (D-A). Ionization potentials of the crown thioethers have been estimated from the CT transition energies. © 1993, Taylor & Francis Group, LLC. All rights reserved.