Communication is one of the things without which corporations cannot to survive on the market. It is important for corporations to communicate, constantly and in a timely manner, with all its stakeholders. In the first part of this paper the theoretical part of corporate communication is shown and consists of: conceptual and theoretical framework, definitions relating to corporate communication (target group, stakeholder, the public and the structuring of corporate environment); corporate identity, image, reputation, personality and culture; organizational models of corporate communication and internal and external forms of corporate communication. With the goal of researching the presence of the theoretical aspects of corporate communication in practise amongst the 20 most successful firms in Croatia, according to the list published in the special attachment “The 1000 greatest” of the weekly magazine “Lider”, a research was conducted that measures degree to which the most successful Croatian companies apply the theory of corporate communication in practice. It is important to emphasize how the digitalization of companies and the emergence of social media have changed communication. Companies should follow trends in communication on social media and actively take part in them if they wish to be successful. In this paper, among other things, it is shown to what degree are the most successful Croatian companies present on social media and how they communicate with their stakeholders through official web sites.