In many unit operations in the chemical, petroleum, pharmaceutical, agricultural, food and biochemi-cal industries the polydisperse particle size distribution (PSD) is crucial to the performance of the operation and/or quality of the product. Nucleation, growth, aggregation and breakage are processes that determine the PSD. In many cases the effect of the flow field on particle morphology and chemi-cal properties is a significant concern in process design and scale-up. Generally, such characteristics are described by using a population balance equation (PBE) with nucleation, growth, aggregation and breakage sub models. The project will deal with effective methods to predict particle size distributions by using the PBE and computational fluid dynamics (CFD). In particular the Direct Quadrature method of moments (DQMOM) as well as the newly developed method Parallel parent daughter classes method (PPDC) will be further developed and tested. Applications will comprise calculation of PSD in bubble col-umns, in fluidised beds as well as droplet formation and evaporation in sprays.