It is shown that the valley-to-peak ratio in gamma-ray spectra bears information about the average path of gamma rays, thansversed in the sample. The measurements of the intrinsic valley-to-peak ratio, due to the response of the detector to gamma rays are presented. The average path in homogeneous sample, estimated from the valley-to peak ration is compared to the path, calculated from the derivative of the efficiency on the attenuation coefficient.