The article presents the problem of the confirmation of treatises between Commonwealth and elector Frederic William of Brandenburg concluded in 1657 during the negotiations in Oliva monastery in 1660 concerning that peace of the war which was waged in northern Europe from 1655. The Brandenburg tried to include these both sides treatises in conclusions of the peace of Oliva to reach guarantees of general peace what could bring to elector the recognition of his release from the Fief in Duchy of Prussia and confirmation of his political independence in this territory. The Swedes didn’t want to agree with this conception because they levelled charges for all the treatises concluded during the war that have been made, in their mind, against them. The confirmation of Prussian case was dealt at the background of other important for Brandenburg questions as for example the delivering the city of Elbing admitted already to the Elector by Commonwealth in treaty of Bromberg in 1657, which the Swedish did not want realize for the same reason as connected with hostile them treatises. At the end after a longer and hard negotiations in Peace of Oliva however was not concluded the special confirmation of release the elector from Fief in Duchy of Prussia and acknowledgment of his independence there but in Peace of Oliva was made a general confirmation all the treatises and agreements concluded during just the finished war what signified also the treatises between the Commonwealth and the Elector of Brandenburg from 1657.