Use of the wave directional frequency response function(wave dF8F), which is composed of conventional frequency response functions, is proposed for identification of the forward and backward travelling wave modes of isotropic rotating disks It is shown that the wave dFRF can be effectively used for identification of the diametrical node numbers associated with modes of interest. Numerical examples of rotating disks are treated to demonstrate the analytical developments. Experiments with a laboratory-rotating disk are also performed to verify the theoretical findings.