Advanced multimedia applications (e.g. based on MPEG-4) will consist of multiple scalable multimedia objects. This scalability enables the application to adapt to different processing capabilities at the end user platforms, hence providing the user with a certain Quality of Service (QoS). Moreover, thanks to the current evolution in run-time reconfigurable computing platforms, reconfigurability is becoming increasingly viable and supports adaptation to the varying complexity of the applications. This paper describes the problem of mapping HW/SW tasks of scalable applications on run-time reconfigurable platforms, built upon an instruction set processor and a run-time reconfigurable hardware, in such a way that the overall quality of service of the applications is maximised. This QoS aware hardware/software (HW/SW) partitioning problem is formulated in terms of an NP-hard optimisation problem for which an approximate solution using a two-step heuristic algorithm is proposed. Experimenta...