The aim of the project was to analyse the vulnerability of the European system to supply shocks. In our paper we evaluate the impact of the evolving market structure on the security of natural gas supply with a special focus on resilience to a supply disruption of piped gas from Russia. Chapter 1 is the assessment of the total potential adjustment capability of the European gas markets today. Estimates are presented for both supply and demand side flexibilities. Chapter 2 investigates the contribution of market interconnectivity to the resilience of the European gas system through EGMM model simulations. Chapter 3 is devoted to the analysis of resilience provided by underground gas storages during supply disruptions. The last chapter is devoted to demand side adjustment to gas supply disruption, focusing on fuel switching in power generation. Both gas-to-coal and gas-to-oil fuel switch flexibility is investigated by EEMM model simulations.