The particle-size dependence of microwave scattering from snow is investigated. Frozen crusts have been analysed, and the microslruclure is described by correlation functions. Relations between the correlation length and various quantities such as ice-intercept lengths or volume-to-surface ratios are checked. The scattering is calculated using the Bom approximation and is linked to the emissivity through the albedo. The model yields good agreement with the microwave data from C to K bands, and the predicted particle-size dependence is verified. The claims that the variance and the correlation length of the permittivity fluctuations are the characteristic parameters are confirmed. Initial uncertainties with respect to the validity of the Born approximation for an air-ice mixture are clarified.