The European Union needs harmonised guidelines to improve the appraisal of large-scale infrastructure dedicated to the Trans-European Networks (TEN); in order to contribute to such guidelines, EU-funded EVA-TREN analyses ex-ante studies and projects outcomes at European level. EVA-TREN’s First Experts’ Workshop brought together experts on large-scale infrastructure planning and operation in the domain of transport and energy. Examination of their practices highlights the following issues: first, the appraisal frameworks EU countries apply for transport and energy projects differ considerably in scope, sophistication, methodology and parameter values; second, the EU Member States share only a small part of all research results; and third, transnational projects are still problematic within the Union. As a result, cost overruns appear in the majority of projects. Investigation of the EU Cohesion Fund programme reveals that one project in four costs more than 20% above budget, while only one in five costs below + 10%. The main problems are modifications to the project (30%) and delays (25%); inadequate cost estimates and technical reasons are blamed for only 20% of cost overruns. Sustainability does not explicitly appear in the appraisal process, even though it is repeatedly quoted as a central aspect of the decision whether an infrastructure should be built or not.