Aims: Despite the syntaxonomic overview of European vegetation, EuroVegChecklist (EVC), there are still considerable gaps in our knowledge regarding the occurrence, composition and distribution of plant communities in parts of Europe, such as the eastern Mediterranean region. This is mainly due to the lack of comprehensive local vegetation surveys. In order to progressively fill these gaps and provide basic data for the assessment and conservation of biological diversity, all vegetation formations of an island were examined. Study area: The island of Lemnos (North Aegean, Greece). Methods: A sample of 877 original relevés was grouped and further classified assisted by TWINSPAN down to alliance and association level. Results: The relevés include approximately 14,000 plant records of 842 vascular plant species, that correspond to about 80% of the island's species pool. A total of 103 vegetation types (associations and equivalents) were classified, that correspond to 36 EVC-standardised classes and 77 alliances, including many associations and several alliances new or confirmed for Hellas. For the first time, a directory and identification key to the plant communities of an eastern Mediterranean island are presented. As a measure of regional habitat diversity, the ratio of numbers of taxa and alliances is offered. The most species-rich habitat types were ruderal pasturelands, cultivated fields and fallows, phrygana and dry grasslands, further saltmarsh and coastal hinterland habitats. The habitats with the highest proportion of indicator species were the dry grasslands and inland cliffs, the coastal dunes and rocks, and the permanently or seasonally wet areas. Conclusions: Comprehensive vegetation surveys on islands (and elsewhere) provide baseline information on habitat diversity, indicator species and conservation priorities. Such studies are needed to review and update the EVC and its species list of classes in regions insufficiently researched so far. Taxonomic reference: Dimopoulos et al. (2013), with updates on the Flora of Greece web, https://portal.cybertaxonomy.org/flora-greece/content). Syntaxonomic reference: Mucina et al. (2016); for exceptions and associations see information in the Suppl. materials 9, 10. Abbreviations: DSCEV = Diagnostic Species of Classes of the European Vegetation; EVC = EuroVegChecklist (Mucina et al. 2016); TWINSPAN = two-way indicator species analysis.