This paper studies the relationship between two themes that have been the subject of recent debate, namely the influence of the lobbies on the economic policy implemented by the Restoration and the opportunity cost of mining policy. The first part takes the form of a comparative study of the liberal mining legislation of 1868 and of the nationalist projects dating from the early years of this century, in order to deter-mine why the mining lobbies defended the liberal legislation, whilst the Spanish industrial bourgeoisie defended the nationalist position. The second part explains the strategy employed by the mining pressure groups to obstruct reform. This strategy demonstrates that the economic policy implemented by the Restoration was the result of the impact of the lobbies on the Government, at the same time as ratifying some of the hypothoses of the theory of the political market. The final part of the paper argues that the country paid a high opportunity cost by tole-rating a significant fraud in mining taxes and by maintaining a very low tax burden on the export of iron, lead and pyrites.