Market research provides insights into various pieces of information about consumers, potential customers, products, price, production, competition and the market. Market research is a necessary tool used before launching new products or services, as well as for the growth or expansion of an existing product range, and, above all, for making business decisions. Market research is a rather complex concept; therefore, this final paper is more oriented towards secondary data sources. Using the descriptive, comparative, compilation, internet and expert literature methods, the term market research, its purpose and objectives, and the process that consists of several phases necessary for the successful conduction of research have been defined. The aim of this paper is to acquaint the reader with various sources of secondary data, as well as the advantages and disadvantages of using secondary data in market research. An analysis and comparison of examples of official, semi-official and unofficial data sources are applied, highlighting their differences, the type of research they are used for, and the degree of authenticity, correctness, relevance and timeliness when collected. With the help of secondary data sources, ideas, thoughts, and/or foundations for further research can be created. When all secondary data sources are exhausted, it is necessary to focus on further data collection from primary sources to further enhance research results and make decisions on the next steps. Proper use of any type of data or source builds the foundation for making proper business decisions. It is important to keep in mind that regardless of the type of source a business chooses, the goal of research and profit generation remains paramount.