This study investigates the frequency dependence of spectral width distributions observed by the SuperDARN HF radars. The evolution of spectral width values with range is shown to be dependent on the operating radar frequency. First, this evolution is clearly pointed out using a multifrequency scanning mode. This study is then generalized and this effect is shown to affect the whole SuperDARN spectral width data set. Several studies are performed in order to determine the dependence of this effect upon season, beam orientation and mean radar orientation.