Legal scholars have regularly focused on the conflict episodes between the Court of Justice and national constitutional courts. We try instead to investigate the techniques that both the Court of Justice and its national counterparts use to develop a hidden judicial dialogue, through which a non-legally bound harmonization is pursued, and mostly achieved. Moreover, we understand these strategies in the light of the notion of comity, and we compare the opposite attitudes kept by the Court of Justice towards national courts and international tribunals to describe its shifting attitude, which is due to its interest in preserving a pre-eminent position in the interpretive competition over EC law.