Site Protection under the Habitats Directive requires that cumulative effects of plans or projects are taken into account in the appropriate assessment according to Art. 6(3). While this assessment has already been subject to an extensive jurisprudence of the Court of Justice of the European Union, it has not yet addressed cumulative effects on sites. The present submission aims to fill this gap. It will be demonstrated that, similar to other constellations, the prohibition of site deterioration provided for in Art. 6(2) of the Habitats Directive is an important complement to the appropriate assessment.