This paper focuses on the addition of commercial wax as flow improver in polymer modified bitumen intended for use in mastic asphalt pavements under Nordic climatic conditions. Different aspects are dealt with. The aim of the project is to make mastic asphalt used in Sweden today (for bridges, parking decks etc.) more environment friendly and easier to handle. However, wax modification must not have any noticeable negative impact on the performance of mastic asphalt at medium and lower temperatures. The project involves laboratory testing of wax and polymer modified binder mixtures as well as mastic asphalt mixtures. Effects of adding two commercial waxes to one polymer modified bitumen have been studied. The results show that both waxes have a flow improving/viscosity depressant impact on the polymer modified bitumen at higher temperatures, indicating a possible lower laying temperature for the mastic asphalt if modified with such waxes. Moreover, there is a stiffening effect at medium and high temperatures (below placing temperature), indicating a certain positive effect on stability. Concerning low temperature performance, there are results indicating some negative impact on crack susceptibility at low temperatures, more by the addition of one of the waxes than by addition of the other. However, it could be concluded that using up to at least 4% of either wax additive will improve workability for the mastic asphalt product under investigation making it possible to lower working temperatures without seriously affecting its good performance in any negative way.