Dual-frequency cloud and precipitation radar systems are being actively developed and installed on different platforms. The use of two radar frequencies (with at least one frequency outside the Rayleigh type of scattering for hydrometeors of interest) allows independent estimates of hydrometeor effective size. With these estimates, radar-based retrievals of such important parameters as cloud mass content or precipitation rate can be potentially performed with better accuracy compared to single- frequency radar measurements. This study presents quantitative assessments of the effects of nonsphericity of ice cloud particles which influence the dual-frequency ratio used for characteristic size estimates.