The main purpose of the study was evaluation of the influence of moisture content of chipped stems of the willow Salix viminalis L. on the granulometric composition of chips acquired in the process of stem fragmentation. The statistical material used in analysis was gathered directly from the willow plantation fields of the Faculty of Production and Power Engineering. The study showed that the fraction of longer chips grows with increase in the moisture level of chipped stems. Analysing the results of the study and the requirements concerning willow chips for fuel it can be concluded that the optimum moisture level of chipped stems should be less than 30%.