A positively operating radiation-sensitive mixture comprising a binder which is insoluble in water but soluble or at least swellable in aqueous alkaline solution, and as a photoactive component a polyfunctional .alpha.-diazo-.beta.-keto ester of the general formula I ##STR1## in which R.sup.1 denotes an aliphatic, cycloaliphatic or araliphatic or aromatic radical having 4 to 20 carbon atoms, in which individual CH.sub.2 groups can be replaced by oxygen or sulfur atoms or by ##STR2## or NH groups and/or contain keto groups, X denotes an aliphatic, cycloaliphatic, carbocyclic, heterocyclic or araliphatic radical having 2 to 22 carbon atoms, in which individual CH.sub.2 groups can be replaced by oxygen or sulfur atoms or by the groups --NR.sup.2 --, --C(O)--O--, --C(O)--NR.sup.2 --, --C(O)-- ##STR3## --NR.sup.2 --C(O)--NR.sup.3 --, --O--C(O)--NR.sup.2 --, --C(O)-- ##STR4## or --O--C(O)--O--, or CH groups can be replaced by ##STR5## in which R.sup.2 and R.sup.3 independently of one another represent hydrogen or an aliphatic, carbocyclic or araliphatic radical,m denotes an integer from 2 to 10 andn denotes an integer from 0 to 2, whereinm-n is .gtoreq.2,is described.The radiation-sensitive mixture is particularly suitable for exposure using radiation of wavelength 190 to 300 nm.