Systemic risk is the risk of a collapse of the entire financial system, typically triggered by the default of one, or more, interconnected financial institutions. In this paper we estimate the systemic risk contribution of Italian listed banks for the period 2000-2011. We follow a methodology first proposed by Adrian and Brunnermeier (2011) and measure banks’ contribution to systemic risk by ΔCoVaR, that measures the contribution of bank i to the financial system VaR when bank i is in a state of distress. We define “the system” as the set of Italian listed banks in the sample. First, we find that the information contained in ΔCoVaR is different from that contained in the VaR. Therefore, regulators should take it into account in order to monitor the systemic risk posed by banks. Second, recent policy debate has focused on the danger posed by large banks and on the need to curb their size. We find that size is indeed the main predictor of a bank contribution to systemic risk. However, in the post-Lehman period leverage is also an important predictor of systemic risk. Consequently, any financial regulation designed only to curb banks’ size could not completely eliminate systemic risk because exactly in crisis times leverage becomes relevant. Hence, we conclude that ΔCoVaR is a very useful policy tool for regulators that can estimate which factors are more relevant in terms of contribution to systemic risk.