Simulation software for the 3D-calculation of the injection moulding process is commercially available for a couple of years now Especially designed for parts of compact geometry more precise simulation results are promised by the principle of three-dimensional meshing of the geometry what stands in contrast to the conventional 2,5D-technique that reduces the real geometry to a shell-shaped model. Here, advantages and disadvantages of both techniques with respect to the simulation of the cavity filling process are compared to each other and set in contrast to the real filling behaviour. Furthermore, the practical "handling" of both simulation systems in the daily development process is estimated.