ABSTRACT: This paper deals with control mechanisms and their functioning in relation to the institutions of the European Union, its bodies, offices and agencies; their decisions, procedure and errors in respect of maladministration. Great emphasis is placed on two institutions that activities contribute to the control of particular European institutions. First of them is the European Ombudsman, that was established as a control mechanism by the Treaty on European Union (Maastricht Treaty), and acting on the basis of complaints from citizens and other entities of the European Union which are registered or established in the territory of the European Union. The second institution of control is the European Parliament, that also performs control activities and receives petitions from citizens and other entities under the Article 227 of the Treaty on the Functioning of the European Union. Both of these control mechanisms belong to the top institutions of the European Union which are dealing with submissions from citizens of the European Union, where particular institutions act contrary to the EU law. The Ombudsman investigates appeals on the grounds of maladministration in institutions and bodies of the European Union. At the same time any EU citizen may appeal with a petition at the European Parliament. The author stresses particular institutes representing control mechanism, doing so within their historical definition as it was in case of Ombudsman, through their initiation to the institutions of the European Union, to the use of them by citizens of the European Union and by other entities that are registered or have been established in the European Union. The paper presents a simplified view on these two institutes of extrajudicial control of the EU institutions.