Together with the Porvoo Diet (1809) the Treaty of Fredrikshamn constitutes the cornerstone for the autonomous Grand Duchy of Finland, and thereby the start of the development which would lead to the revival of Finnish language and culture, and ultimately in 1917 to Finland's independence.
Also for Sweden, the treaty turned out to be ultimately beneficial. During the negotiations, Swedish representatives had endeavoured to escape the loss of the Åland islands, "the fore-posts of Stockholm," as Napoleon rightly described them. (The Åland islands were additionally culturally, ethnically and linguistically purely Swedish, but that was of no significance at that time.) In the course of the 19th century it would also turn out that the Åland islands were a British interest, which after the Crimean War led to the de-militarization of the islands according to the Åland Convention included in the Treaty of Paris (1856). Instead of the Åland islands, Sweden came to retain vast areas in the far North, already conquered by the Russians, where later important iron ore and hydropower were to constitute the basis for Sweden's rapid 20th century industrialization.