Most EU member states have a documented policy on eHealth. Documented follow-up and evaluation policies to assess reaching of the set aims, as well as evaluating outcomes of implemented systems at a national level are, however, rare. Methodologies for large scale information system assessment and evaluation are poorly established. In the workshop, the Finnish evaluation plans for the National Health Information System (NHIS) are used as a case in the workshop to reflect on core issues and challenges in large-scale evaluation for supporting system development, implementation and positive impacts. The results of the discussions are documented to be used in further refinement of the Finnish evaluation methodology and for enhancing networking of respective parties in different countries. The results will also benefit participants including policy makers, developers and researchers of national eHealth systems in pursuit of national evaluation activities.