The judges are assisted by eleven Advocates General, whose number may be increased by the Council if the Court so requests. The Advocates General are responsible for presenting a legal opinion on the cases assigned to them. They can question the parties involved and then give their opinion on a legal solution to the case before the judges deliberate and deliver their judgment. The intention behind having Advocates General attached is to provide independent and impartial opinions concerning the Court's cases. Unlike the Court's judgments, the written opinions of the Advocates General are the works of a single author and are consequently generally more readable and deal with the legal issues more comprehensively than the Court, which is limited to the particular matters at hand.
The opinions of the Advocates General are advisory and do not bind the Court, but they are nonetheless very influential and are followed in the majority of cases. In a 2016 study, Arrebola and Mauricio measured the influence of the Advocate General on the judgments of the Court, showing that the Court is approximately 67% more likely to deliver a particular outcome if that was the opinion of the Advocate General. As of 2003, Advocates General are only required to give an opinion if the Court considers the case raises a new point of law.
According to Article 255 TFEU the judges and advocates-general are appointed by common accord of the governments of the Member States after consultation of a panel responsible for assessing candidates’ suitability.
The Registrar is the Court's chief administrator. They manage departments under the authority of the Court's president. The Court may also appoint one or more Assistant Registrars. They help the Court, the Chambers, the President and the Judges in all their official functions. They are responsible for the Registry as well as for the receipt, transmission and custody of documents and pleadings that have been entered in a register initialled by the President. They are Guardian of the Seals and responsible for the Court's archives and publications.
The Registrar is responsible for the administration of the Court, its financial management and its accounts. The operation of the Court is in the hands of officials and other servants who are responsible to the Registrar under the authority of the President. The Court administers its own infrastructure; this includes the Translation Directorate, which, as of 2012[update] employed 44.7% of the staff of the institution.
The Court can sit in plenary session, as a Grand Chamber of fifteen judges (including the president and vice-president), or in chambers of three or five judges. Plenary sittings are now very rare, and the court mostly sits in chambers of three or five judges. Each chamber elects its own president who is elected for a term of three years in the case of the five-judge chambers or one year in the case of three-judge chambers.
The Court is required to sit in full court in exceptional cases provided for in the treaties. The court may also decide to sit in full, if the issues raised are considered to be of exceptional importance. Sitting as a Grand Chamber is more common and can happen when a Member State or a Union institution, that is a party to certain proceedings, so requests, or in particularly complex or important cases.
The court acts as a collegial body: decisions are those of the court rather than of individual judges; no minority opinions are given and indeed the existence of a majority decision rather than unanimity is never suggested.