The single-scattering properties of cirrus clouds depend not only upon the ice water path andthe size of the crystals, but also upon the crystal shape. A novel parameterization has been usedto explore the differences in broadband short-wave radiation due to various crystal habits. Thedifferences in the net-fluxes are found to be appreciable, both at the tropopause and at thesurface. They reach values up to the order of several 10 Wm-2 for mid-latitude and up to some 100W m-2 for tropical cirrus. The largest differences are found for an intermediate range ofoptical depths and the optical thickness of natural cirrus happen to be in this intermediaterange. The absorptivity of the cirrus cloud is independent of the crystal habit, nevertheless, thechange in the cloud’s reflectivity has an impact on the tropospheric absorption and, thus, theenergy absorbed by the troposphere depends on the crystal habit. The sensitivity of the resultswith respect to surface albedo and solar zenith angle has been investigated. A lower zenithangle enhances the differences found for the various habits, and this effect is even amplified bya high amount of water vapour as it may be found in the tropics. A comparison with observationsfrom ICE’89 reveals that the large differences in the modelled fluxes are comparable to theuncertainty in the measurements. Despite this observational difficulty, the large differences inSW fluxes emphasise the importance of the crystal habit for radiation schemes.