ENThe article reviews various sources of educational data (e.g., international large-scale studies, data registers) and their use for policy decisions and research in Lithuania. It has been shown that a lot of data has already been collected and that more is being accumulated. Up to 20 percent of the information gathered is used for policy purposes and even less in research. It is noted that most of the data collected is useful for the economic paradigm. The chapter presents case study showing that national population-based studies and international achievement studies may send different messages and cannot be considered in isolation. [From the publication]