The European dimension of administrative law is the focus of a flurry of initiatives aiming to investigate similarities and differences, and to shape common legal scenarios. A codification of the administrative procedures of the EU has been envisaged by the European Parliament in its resolution of February 2013. A broader proposal of codification, including rule-making and contractual procedures, has been elaborated by ReNEUAL and has been discussed in a series of workshops in 2015.The issues that arise are both practical and theoretical:- it is important to understand whether the method traditionally followed by the European Court of Justice in order to identify the principles that are general and common to national legal systems, only applies when all those systems recognize such principles;- whether national systems of public law share the same idea of what an administrative procedure is is another question;whether the specific principles governing administrative procedures, such as the right to be heard and the duty to give reasons, are the same is still another question;- finally, if any commonality exists, the question that arises is whether it is limited to the level of general principles of law or it includes the which govern procedures.The research project is innovative on grounds of method, because: - it aims at ascertaining whether, and the extent to that, the well-established methodology developed under the ‘Common Core of European Private Law’ project can be applied to EU administrative law;- it permits to distinguish between ‘operative rules’, ‘descriptive formants’, and ‘meta-legal formants’;- it also allows to understand whether the specific nature of the interests recognized and protected by the rules of public law require legal methodologies that are distinct and distant from those of private law.