In quasi-one-dimensional organic crystals, the relaxation time as a function of carrier energy can exhibit, under certain conditions, a rather high and sharp maximum. It is shown that this maximum and its position on the energy scale influence the electrical conductivity and electronic thermal conductivity in different ways. First, the electrical conductivity is considerably increased. The electronic thermal conductivity is also increased, but to a lesser extent due to the narrower energy interval of carriers that contribute to energy transport. Second, both the electrical conductivity and electronic thermal conductivity achieve maximums, but the latter is displaced to higher carrier concentrations in comparison with the maximum of electrical conductivity. As a consequence, the Lorenz number is decreased for some range of carrier concentration and is increased in other ranges. It is important that there is a large interval of carrier concentrations where the Lorenz number is significantly diminished and the Fermi level can be moved up to this interval. The Lorenz number may be diminished considerably in comparison with ordinary materials. This is favorable for increase of the thermoelectric figure of merit.