The analysis of the importance of different types of regional innovation systems must take place within a context of the actual knowledge base of various industries in the economy, as the innovation processes of firms are strongly shaped by their specific knowledge base. In this paper, we shall distinguish between two types of knowledge base: analytical and synthetic. These types indicate different mixes of tacit and codified knowledge, codification possibilities and limits, qualifications and skills, required organisations and institutions involved, as well as specific competitive challenges from a globalising economy, which have different implications for different sectors of industry, and, thus, for the kind of innovation support needed. The traditional constellation of industrial clusters surrounded by innovation supporting organisations, constituting a regional innovation system, is nearly always to be found in contexts of industries with a synthetic knowledge base (e.g. engineering-based industries), while the existence of regional innovation systems as an integral part of a cluster will normally be the case of industries-based on an analytical knowledge base (e.g. science-based industries, such as IT and bio-tech). In the discussion of different types of regional innovation systems five empirical illustrations from a Nordic comparative project on SMEs and regional innovation systems will be used: the furniture industry in Salling, Denmark; the wireless communication industry in North Jutland, Denmark; the functional food industry in Scania, Sweden; the food industry in Rogaland, Norway and the electronics industry in Horten, Norway. We argue that in terms of innovation policy the regional level often provides a grounded approach embedded in networks of actors acknowledging the importance of the knowledge base of an industry.