Whilst task models are perceived as critical artifacts within User Centered Design methods, task models development is often considered as a resource and time consuming activity. Structuring techniques can support handling issues such as reuse and scalability and can improve analysts’ productivity and the overall quality of models. In this paper we propose (based on the notation of the HAMSTERS project) several means to structure task models and present how they can be used in order to increase reusability and scalability in task models. Besides sub-models and sub-routines, generic components are described. These mechanisms are duly illustrated within a project for the ground segments of satellite missions. This paper shows, by example, how such elements look like and how both readability and quality of models is improved by their use.