The effect of changes in surface tension and degree of liquid jet break-up as well as final moisture content of the bed on changes in particle size distribution during wet drum granulation was described in the paper. The tumbling bed of loose material (silica flour) was wetted at a constant volumetric flow rate, using a system of two pneumatic spray nozzles. Different values of surface tension of the binding liquid (distilled water) were obtained due to the application of a surfactant Rokanol L4P5. In every trial samples of the feed were taken from the drum at specified time intervals and on this basis particle size composition was determined.