Dual-wavelength radars can provide, in principle, extra information to help in the estimation of precipitation. One method would be to use the differential attenuation measured between their two frequencies as an indication of rain intensity. For S- and X-band radars, the attenuation of the longer wavelength by precipitation can be neglected, whereas for the shorter wavelength it can be significant enough to be detected. The attenuation introduced by rain at X-band frequencies is widely regarded in the literature as a good estimator of the intensity of precipitation. However, after analyzing two multi-year disdrometer datasets we find a surprising proportionality between attenuation and reflectivity for higher intensities of precipitation (Z > 40dBZ). It is precisely at these values of intensity that current S- and X-band dual-wavelength radars can measure X-band attenuation. Our finding limits the possibility of using attenuation as a second parameter at these radars, since the X-band attenuation they can measure would be almost equivalent to reflectivity. Nevertheless, radar-measured attenuation could be used for radar calibration. In this work, we present preliminary results obtained from a limited dataset composed of two days of dual-wavelength radar data and simultaneous disdrometer measurements.