The Greenland and Svalbard Caledonides make up an important part of the Palaeozoic Caledonian orogen, and preserve a complex history of Palaeoproterozoic arc accretion, Proterozoic to Palaeozoic sedimentation within various basins and extensive magmatism, metamorphism and deformation during the Caledonian orogeny. In this summary, the current understanding of the structure and lithological content of the Greenland and Svalbard Caledonides is first reviewed, and open questions are highlighted. The Greenland Caledonides are divided into three different segments, and the term terrane is abandoned for the Svalbard Caledonides. Then, other Caledonian fragments in the Arctic region are discussed, including Bjørnøya, Pearya and Cordilleran terranes and parts of the Barents Shelf. Finally, a regional synthesis covering the geological evolution of the Greenland and Svalbard Caledonides from the Palaeoproterozoic to the end of the Caledonian orogeny is presented and controversial issues and open questions are discussed.