The surface potential technique was used for investigation of donor, acceptor and mixed monolayers, containing molecules suitable for deposition of conducting LB films. It is shown that the donor and acceptor monolayers are neutral at the air-water interface. Big positive values of surface potential in the case of donor molecules are explained by peculiarities of dipole depolarization near the surface of the water and by charge transfer salt formation with water-soluble impurities. The dipole moment arising due to charge transfer between donor and acceptor molecules in mixed monolayers is parallel to the layer plane. Other details of charge transfer complexes or salt formation in the mixed monolayers are discussed.