The goal of this paper is to describe and compare key activities and operations of credit rating agencies of the United States of America and the European Union. The analysis was conducted using secondary sources. The paper begins with a theoretical description of the historical development of credit rating agencies, defining the notion of credit rating agencies and key concepts related to rating, and also describes the features of agencies with their advantages and disadvantages. The second part describes the regulatory reports and the credit rating agencies market situation in United States, through the characteristics and operations of the credit rating agencies themselves, to highlight the dominance of credit rating agencies in the financial market and their relationship with the economic crisis. The following section describes the regulatory requirements of the European Union and the structure and activities of rating agencies in that market. Finally, a brief overview of the situation in the Republic of Croatia is given. The analysis showed the great impact of ratings on the movement and trading in the financial market, in which all participants, from issuers through intermediaries to investors, benefit from credit ratings. Further analysis and comparison of the data showed a great similarity in the business and performance of credit rating agencies in the markets, with a key competitive dominance of world agencies such as Standard & Poor's, Fitch Ratings and Moody’s, with a minimum market share of rating agencies of certain countries in the European Union. such as Germany, Spain. Through the growing ratings gains, these global rating agencies are also making huge profits as information technology and advisory service providers. Comparing the regulations implemented by the Securities and Exchange Commission and the European Securities and Markets Authority (ESMA) as supervisory authorities of rating agencies, one can see the present problems in the oligopoly market and the need to reduce conflicts of interest and increase transparency in both markets. In addition, through an analysis of the rating process of the state, the corporation and the financial instrument, the similarities, advantages and disadvantages of the rating methodology used by the rating agencies were identified. In the case of the Republic of Croatia, the ratings are assigned by External Credit Rating Institutions registered with the Croatian National Bank.