Most EU Member States have a documented policy on eHealth. Documented follow-up and evaluation strategies for assessing whether national level systems have reached their set aims and outcomes are, however, rare. Methodologies for large scale information system assessment and evaluation are poorly established. This article describes the approach used to generate the Finnish National Health Information System (NHIS) evaluation plan. The core elements of the plan are illustrated, discussing also challenges and solutions in implementation. The article is based on NHIS evaluation planning project [15] and its presentation in the MIE workshop in Sarajevo in 2009 [16], where core issues and challenges of large-scale evaluations were discussed using the Finnish NHIS evaluation plan as a frame of reference.The Finnish plan offers other countries tools with which to assess their own plans and generate national methodologies for NHIS evaluation.