This study focuses on one of the basic questions of Luhmann’s socialtheory relating to the description of modernity, namely, on the characteristics of organisations, even more specifically, it is aimed at gaining new recognitions concerning the relationships between the functional subsystems and the organisations. Organisations, one of the most important levels of today’s society, is analysed in the context of Luhmann’s general social theory. The approach taken in the study originates from Luhmann’s analysis of subsystems during the lateperiod of his work. The author argues that vertical relationships between subsystems make up a typical feature of modern society as well. In its analysis of the organisations of modern society this study works out an interpretation of the relationship between stable and fluid structures in the process of communication, highlighting the frequently or continuously changing ‘rationality preference’ oforganisations and it argues for the necessity a more complex analysis of organisational communication. At the same time the study points out by analysing the organisation’s system level that vertical segmentation is a characteristic of the entirety of sociality besides the horizontal structure.