Green infrastructure has been strongly promoted by the EU as a concept of landscape protection, with special emphasis on the importance of its implementation in spatial planning. Despite that, GI has not been implemented in the spatial planning system of the Republic of Croatia. The implementation of GI would, in this regard, certainly contribute to a more integrated approach to spatial analysis, and thus to the improvement of its ecological, social, morphological and economic characteristics. The potential for its formation as a system is also visible on the example of the City of Zabok, which is the subject of research in this paper. The area of Zabok is characterized by an economic zone and a dense network of roads. With increasing economic development, construction areas are increasing, thus fragmenting valuable open spaces. In contrast, there are many types of open spaces that are mono-functional or completely non-functional and require some improvement. This paper's goal is to attempt to achieve a correlation between GI as a system with the existing, but also with the potential characteristics for Zabok’s open spaces. At the very beginning of the paper, taking in consideration the relevant literature, different views on the concept of GI have been defined; all the benefits it can provide for a human and his environment, elements it contains, with emphasis on elements at the city level. Here GI is observed from a landscape-ecological approach, therefore its elements are identified with open spaces that are characterized by the structure of purpose (from the spatial and ecological aspect), well-being for human and his environment, and the level of interconnectedness. Inventarisation and analysis were conducted by both indoor and field work, with an emphasis on the establishment and analysis of spatial and cartographic data. The inventorisation included an analysis of natural and anthropogenic factors that are thought to have influenced the current state of open spaces. Their influence was studied by analyzing the genesis of the morphology of gray, blue, and green infrastructure. Insight into the state of development trends and potential risks, was obtained by analyzing the spatial planning documentation. Summarizing the knowledge about the existing characteristics of the elements of GI and possible influences, a proposal is given for the development of GI according to different levels of implementation. These include the proposal of measures for the development of the GI for the wider spatial coverage of Zabok (with associated settlements) and its broader spatial context and the proposal of guidelines in the form of a concept for the development of the GI for the narrower spatial coverage-the city of Zabok. The development of the concept was preceded by the typology of space and the evaluation of each type according to the basic functions of GI. The purpose of the evaluation was to define the existing and potential characteristics of the space. Based on their difference, the level of potential that these spaces have for the development of GI was defined. The development concept is based on the existing valuable open spaces and the proposal of guidelines for those spaces where a high level of potential has been determined.