Agent for lightening keratin fibers containing in a cosmetic carrier (1) at least one cationic 2-acylpyridinium derivative of formula (I), wherein R is a C1-C6 alkyl group, a C2-C6 alkenyl group, a C2-C6 hydroxyalkyl group, a C1-C6 alkoxy C2-C6 alkyl group, a carboxy C1-C6 alkyl group, an aryl C1-C6 alkyl group, a heteroaryl C1-C6 alkyl group, a mono- or di-(C1-C6 alkyl)amino C2-C6 alkyl group, a 3-oxobutyl group, a 2-oxopropyl group, an aryl group or a heteroaryl group, R′ is a C4-C4 alkyl group, a C2-C6 hydroxyalkyl group or a C1-C6 alkoxy C2-C6 alkyl group, and X− is a physiologically acceptable anion, (2) at least one alkyl ether sulfate, and (3) an oxidizing agent, especially hydrogen peroxide.