Concentrated storage stable aqueous solutions (S) comprising components (a), (b) and (c), wherein component (a) is at least one optical brightening agent of formula (1), in which the anionic charge on the brightener is balanced by a cationic charge composed of one or more cations selected from the group consisting of hydrogen, alkali metal cation, alkaline earth metal cation, ammonium, ammonium which is mono-, di- or trisubstituted by a C1-4 linear or branched alkyl radical and ammonium which is mono-, di- or trisubstituted by a C1-4 linear or branched hydroxyalkyl radical, and the concentration of component (a) is 0.08 to 0.3 mol per kg, based on the total weight of the concentrated storage-stable aqueous solutions (S), component (b) is at least one inorganic salt (SA), in a concentration of 2 to 15% by weight, based on the total weight of the concentrated storage-stable aqueous solutions (S), and component (c) is water, in a concentration of 10% to 88% by weight, based on the total weight of the concentrated storage-stable aqueous solutions (S).