This paper presents a new method for extracting the wavelength and losses of dispersive lossy planar lines from measurements made up to 40 GHz. It requires only two lines, differing by their length, while the LRL method necessites four elements. This new method has been successfully tested on microstrips, slotlines and coplanar waveguides. The results confirm the validity of the method and the accuracy ofthe models developed by the authors for those lines. From the results, a method has been designed to measure the dielectric constant of the substrates, with a very good accuracy up to 40 GHz.