This paper reconsiders the effects of fiscal federalism on the size of government: the Leviathan hypothesis, suggesting a negative relationship between fiscal decentralization and government growth, has been recently enriched by theoretical and empirical research that points out at the importance of distinguishing between grants and own resources to gauge the effects of fiscal decentralization on public sector size; moreover, several additional economic, demographic and political control variables have been proved to be empirically relevant. This paper improves on this literature by distinguishing long from short run relationships by means of appropriate panel cointegration techniques.JEL code: H11, H53, H77