Background Marine habitats have greatly regressed in the Baltic Sea due to extensive eutrophication and the influence of increased amounts of toxic substances. The Finnish exclusive economic zone (EEZ) was established recently, after the designation of the Natura 2000 network, and only a few preliminary surveys of underwater habitat types have been made in these areas. Key marine habitat types need to be investigated to assist compliance with the Habitats Directive. Objectives The objective of the FINMARINET project was to produce a coherent overview of marine habitat types, as listed in the Habitats Directive. In particular, the aim was to produce inventories and maps for underwater habitat types and their flora and fauna in key marine Natura 2000 sites, and then use the field-collected data in GIS distribution modelling for habitats and species. Other planned actions included supporting the implementation and proposed extension of the Natura 2000 network in marine areas through the production of new information for the Ministry of the Environment; the construction of an Internet-based information service to provide marine spatial data and information for experts and the general public; and to raise public awareness of marine habitats and their conservation. Results The LIFE project produced a coherent overview of Habitats Directive marine habitat types, and the species that characterise them, through field inventories, including geological and biological inventories of the seafloor, and cartographic information. The geological inventories covered 787 km2 of seafloor, combining acoustic-seismic methods with sediment samples taken at 107 sites and drop-video done at 106 sites. The biological inventory data was acquired from a total of 22 886 drop-video transects from a boat, 652 remotely-operated robot camera (ROV) video transects in deeper water, 250 dive transects and 416 benthic samples. The field data delivered by the project is the largest produced by any project so far in Finland. GIS and statistical modelling techniques were subsequently used to combine the geological and biological inventory data. The results of this included geological maps and maps of Habitat Directory Annex I habitats, EUNIS habitat types and predicted distributions of key species and community types. The maps of species occurrence and of the marine Natura 2000 habitats in the project target areas presented information not previously available. The FINMARINET project enabled the partner organisations to greatly develop their modelling capacities, to serve similar activities in the future. An Internet-based information service was constructed to provide marine spatial data and information for experts and the general public. Public awareness of marine nature has been raised by promoting education on marine biodiversity issues. Information produced by the LIFE project has been disseminated at multiple levels, for example, on the project website, via the Layman’s report and project brochure, through technical publications, and at four seminars/conferences and seven training events. The success of the FINMARINET project has also increased the number of experts on marine nature in the Northern Baltic Sea, established productive national and international networks of excellence in the field of marine nature survey, and generally improved awareness of Finnish marine nature. Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).