Flow induced fibre orientation determines the mechanical properties of short fibre reinforced thermoplastics. Simulation of mechanical properties of components through the coupling of flow simulations, fibre orientation simulation and structural FEM is widely used in engineering. It is commonly assumed in flow simulation that the rheological properties and thus the flow of the molten plastic are independent of the fibre orientation during flow. However, for high fibre concentrations this can be a false assumption. In this work, to investigate the importance of this issue, rectangular film gated plates of the same PA12 material with 15, 30 and 50 wt% fibres have been injection moulded, and the fibre orientation in selected areas determined using ƒÝ-CT. Significant influence of fibre concentration on fibre orientation is observed. The effect of increasing concentration includes increasing core layer thickness, slower core layer development, coherent rotation of fibres in core layer and higher degree of orientation in both core and shell layer. The observed effects of fibre concentration are qualitatively in good accordance with theories for fibre orientation ¡V flow coupling.