The coordinated administrative decisions, introduced most recently by the EU legislation, do represent a new phenomenon in the framework of European Administrative Law. While being issued by the competent administrative authorities of the Member States, the applicable Union’s legislation stipulates for coordinated administrative proceedings to be conducted and for decisions of the competent national authorities to be issued at the same time. Consequently, the EU law provides for mutual transnational effects of coordinated decisions. At the same time, the Union’s legislation provides for a competence of an executive agency to issue a decisions in the case, national administrative authorities will not provide so. However, the applicable Union’s legislation remains silent concerning several crucial aspects of the application of national procedural law vis-á-vis these coordinated administrative decisions. In practical terms, the concept of mutual transnational effects implies several serious questions regarding the legal effectivity of these decisions. Further, there are further serious questions regarding the legal consequences of cancelling or amendment of these decisions by any extraordinary means of the administrative review. Consequently, answers are to be found in the provisions of national law governing the administrative proceedings. This article aims at identifying the most serious issues arising from this new model of administrative decisionmaking.