Carbonation mud contains CaCO₃ and aggregated or adsorbed substances from sugar beet raw juice. The precipitate can be characterised as a polydisperse system. Large volumes of carbonation mud predetermine its use as a fertilizer. Other possibilities of utilization are tested – e.g. addition in animal feed mixtures, application as paper, plastic and rubber fillers, and usage for the building industry and for desulphurization of combustion gases. Re-using of carbonation mud in sugar technology enables to decrease lime consumption in a sugar factory and to minimize carbonation mud production. It involves economic aspects and environmental effects (decreasing lime stone mining and limiting carbonation mud production). For these feasible internal or external applications of carbonation mud it is necessary to know size distribution in advance. The research work was aimed at particle size distribution measurement of carbonation mud suspension, which was separated in hydrocyclones used in MZ-technology. This low-cost sugar juice purification method is based on re-using carbonation mud and following separation of mud particles. Authors have chosen an image analysis method (system LUCIA) combined with microscopic observation for particle equivalent diameter determination. At first it was necessary to work out original measuring methodology for carbonation mud, it includes choosing suitable object-lenses, design of lightning, preparing suitable subroutine in which values of contrast and threshold are defined, etc. From these size data the particle size distribution was calculated. We detected that the industrial method for the preparation of input mud suspension was not fine enough and an amount of small particles increased in comparison with the unfiltered 1^st carbonation juice. Bottom output suspension of hydrocyclones was of worse quality with small particles than the 1^st carbonation juice as well. Hydrocyclones did not affect small particles. A normality of size distribution of particles from input and output suspensions in MZ-technology was tested. It can be characterised by normal distribution function for volume fraction x_V or by log-normal distribution function for frequency of particles, as to input particles and upper output particles of hydrocyclones. The measured results will be groundwork for next carbonation mud applications.