This paper is a part of larger research project on the role of the 30 largest firms in the Nordic countries. By examining the changes in the role of top 30 firms in the Finnish economy we aim to reveal some essential features of the structural transformation in the economy. From the national economy point of view these firms are in a crucial position. Almost all of them are multinationals, operate in several countries, and make influential decisions on trade and location of production. The analysis suggests that top 30 firms account for a substantial portion of business sector employment and value added in Finland. Moreover, the role of these large companies is particularly significant in foreign direct investment and in research and development. Our data however indicate that their role in the Finnish economy in terms of output and employment shares seems to have decreased during the recent decades. Yet, it is an open question to what extent large firms have reorganized their operations in such a way that they do not directly show up in their own output and employment data.