In this work the influence of the cooling fin shape on the pressure drop caused by flow resistance of a heat sink is studied. A new manner to optimise heat sinks is developed, bringing the emphasis not only on maximum heat transfer flux, but also on minimum flow resistance. The study is done numerically using the computational fluid dynamic software FLUENT. The results show the advantages of using aerodynamic shaped fins if the Reynolds number, based on the spacing between the cooling fins, is greater or equal than about 800. Some preliminary profile shapes are suggested. The authors consider this research as a quite unique approach as compared to other research where the flow resistance has not been taken into account.