In 1998, the European Commission decided to institutionalize European sectoral social dialogue (ESSD) committees under a new harmonized form. As of 2010, there are 40 sectors with a sectoral committee. A recent Commission assessment suggested that there is a direct correlation between the effectiveness of ESSD and that of social dialogue on a national level. This article analyses in greater detail the relationships between the European committees and national-level social partners, showing that these relationships play a decisive role in the ability of ESSD to work efficiently. The article examines four dimensions of this 'vertical coordination': the representativeness of the European social partners; the Europeanization of interests; national players' involvement in the ESSD committees and, finally, the implementation of joint texts. As these four dimensions are by no means autonomous, the article briefly examines their interaction in its last section, showing that this can fuel either a vicious circle hindering ESSD or, by contrast, a virtuous circle facilitating it.