Recently, the importance of the regional innovation system issue has grown considerably, especially because many regions are currently working on the implementation of an innovation strategy that would create and support innovation activities and processes. In this context, it should be noted that extensive support for the processes of a regional innovation system (or strategy) is frequently associated with the use of public funds. To ensure maximum efficiency for the allocation of resources, it is necessary to have a method that is able to analyse regional innovation systems and their level of development. Such a method has not yet been published. The aim of this paper is to use the weighted sum method to evaluate the effects arising from the existence of regional innovation systems as well as to determine their level of development. This is a completely new approach for determining how developed a regional innovation system is in practice. This case study applies this method using four Czech regions.