The character of Paolo Roberto is an actual person. He is a former boxer and television chef who has also dabbled in politics. He played himself in the film based on the book.
In the first part of the book, Salander is exploring Dimensions in Mathematics apparently written by L. C. Parnault and published by Harvard University Press in 1999. On February 9, 2009, Harvard University Press announced on their website that this book, as well as the author, is purely fictitious.
The mysterious Karl Axel Bodin, in whose house Salander finds Zalachenko and Niedermann, is a historical name. Bodin was born in Karlstad and later moved to Sundsvall. He went to Norway to join the Waffen-SS; at the end of World War II, he was attached to the country's branch of the Gestapo. At the war's end, Bodin and another Swedish volunteer stole a car in an attempted escape to Sweden. The car's owner saw the theft, and soon a gunfight erupted in which the car owner and Bodin's friend were shot. Bodin left his friend behind and crossed the border.