Seventeen municipalities participate in the cooperation in the Helsinki region:
- Cities in the Metropolitan Area: Helsinki, Espoo, Vantaa and Kauniainen
- The so-called KUUMA municipalities: Järvenpää, Nurmijärvi, Tuusula, Kerava, Mäntsälä, Pornainen, Hyvinkää, Kirkkonummi, Vihti and Sipoo
- Partnership municipalities: Porvoo, Lohja and Siuntio.
The common goal of the participating municipalities is to develop cooperation and advocacy. The cooperation is based on the shared vision of the municipalities in the Helsinki region regarding the challenges facing the region and the shared will to contribute to the development of the region.
Regional cooperation focuses in particular on land use, housing and transport, joint interest representation of the region and if necessary, regional services.
The First Chairs of the Municipal Councils and Boards of agreement and partnership municipalities, a total of 34 elected representatives and additional members elected by the Cooperation Assembly, participate in the Cooperation Assembly. The Cooperation Assembly is held approximately 2–3 times per year as required.
The Helsinki Region Cooperation Agreement was renewed during the 2017–2021 council term and is valid until further notice. The first cooperation agreement for the Helsinki region was signed in 2005.