Brightening agents with cationic 3,4-Dihydroisochinoliniumderivaten and hydrogen peroxide

The invention provides a means for lightening of keratin fibers, characterized in that it in a cosmetic carrier, at least one cationic 3,4-Dihydroisochinoliniumderivat the following general structure (I), wherein · The radical R 1 represents a C · Alkylamino group, the radicals R2, R3 and R4 are independently a hydrogen atom, a hydroxy group, an amino group, a di (C · The anion X hydrogen peroxide includes the use of this agent for brightening hair, as well as a corresponding method.