This is the author pre-print version. The final version has been published in the Journal of Legislative Studies, Vol. 23, issue 2 Abstract:Regional parliaments can today try to shape EU policy-making via a range of domestic and European channels. In the context of a renewed interest in the subnational level, this article aims to address three core questions: Have regional parliaments really been empowered by the EWS provisions?Which factors explain differences in strength and mobilization? Finally, what kind of a role do regional parliaments play in EU policy-making today, now that they have had several years to react to the trend towards multi-level parliamentarism? The article argues that regional parliaments do indeed have the potential to contribute a distinct perspective to EU policy-making, even if their current level of activity is still low. It distinguishes six particularly important factors contributing to the empowerment and mobilization of regional parliaments: whether the new powers are formally protected, the previous constitutional strength of the regional parliament, the absence of second chambers that represent regional governments, good executive-legislative cooperation, resources and experience.