Jaw crushers are commonly-used machines in aggregate production. The aim of the research is to present a model which is able to predict particle size distribution in jaw crushers and to provide a new method for effectively controlling the quality of crushed product. The object of study was a domestic PEF 400×600 jaw crusher. A performance model was developed based on the standard mass balance formulation and chamber dividing results. Some important parameters that influence the particle output of the crushers were taken into account in the model. The variations of the particle size distribution resulting from changes in the eccentric shaft rotational speed and the parallel strip length were investigated.