The paper empirically verifies whether countries that use environmental taxes relatively more are also more engaged in environment policies or, alternatively, that they use such taxes for general expenditures purposes – a situation revealing at worst a Leviathan behavior by the government or, at least, an inefficiency inherent to the instrument. We examine the EU-27 countries that have committed themselves to attain a set of individual targets of reduction of greenhouse gas emissions by 2020. A dynamic system of simultaneous equations shows that neither such commitment positively affects the resort to environmental taxation, nor that these taxes help attaining the GHG reduction targets. To bring evidence to bear on the Leviathan vs. inefficiency interpretation of these results we further examine whether countries that use environmental taxes more also spend more for the protection of the environment. As a negative correlation instead emerges, our analysis leans towards the interpretation that there is a Leviathan behind environmental taxes.