Mega structures for CO₂ storage, such as the Utsira formation in the North Sea, could theoretically supply CO₂ storage capacity for several countries for a period of several decades. Their use could increase the cost-effectiveness of CCS in a region while minimizing opposition from the public to CO₂ storage. However, this will not only depend on their potential available capacity to store CO₂ flows but also on the cost effectiveness of such an option within national portfolios of mitigation measures. This article shows key results of a research project aiming to assess the potentials and costs of storing CO₂ in the Utsira formation for the time period 2015-2050. Countries included in the analysis are Denmark, Germany, Norway, the Netherlands and the United Kingdom. The starting point of the analysis are the national MARKAL and TIMES models developed for each country together with the 27 region Pan European TIMES model (PET). In the models scenarios, assumptions and parameters that are not country dependent (e.g. costs related with CO₂ capture technology development) have been harmonized. The results indicate that with stringent climate targets, CCS appears as a key mitigation option in the national portfolio of measures. Within the CCS portfolio, storage of CO₂ in the Utsira formation can indeed be a cost effective option for North Europe and it represents a valuable CO₂ storage option at the regional level. For instance, the United Kingdom will profit from the comparably short transport distance to Utsira while the Netherlands utilise the Utsira formation due to limited domestic low cost storage fields and the use of the country as a regional hub for CO₂. In Germany and Denmark, the competitiveness of CO₂ storage in Utsira is determined by the availability of domestic onshore saline aquifers. If these aquifers are not used, Utsira gains as competitive storage option. The main limitation for the common use of the Utsira formation appears, from a modeling point of view, to be the maximum annual injection rate for CO₂ that has been assumed in the project (150 Mt CO₂/yr).