A technique using 3 omega-method with a wide-frequency range from 0.5 Hz to 0.5 MHz was developed to determine simultaneously the thermal conductivities of individual layers in a two-layered structure. The technique utilizes 3 omega measurements in high and low frequency ranges separately. To evaluate the validity and accuracy of the technique, we performed measurements on a double-layered specimen consisting of a SiO2-film on a Si-substrate, and found that the measured conductivities of both the film and substrate agree well with literature values. Uncertainty analysis was given finally. This new technique overcomes a critical shortcoming of conventional techniques, which cannot measure the thermal conductivity of both film and substrate simultaneously. (c) 2007 Elsevier B.V. All rights reserved.