The invention relates to novel N-substituted imides and polymerizable compositions comprising these N-substituted imides. The invention further relates to the use of N-substituted imides as polymerization initiators. The imides are compounds of the formula (I) and (II) wherein n is 1 or 2; m is 1 or 2; R.sub.1 and R.sub.2 are each, independently of one another, hydrogen, C.sub.1-C.sub.18alkyl, C.sub.1-C-.sub.18alkenyl C.sub.6-C.sub.14aryl, aralkyl, C.sub.5-C.sub.12cycloalkyl, each of which may be substituted by halogen, C.sub.1-C.sub.4-alkyl, hydroxy, C.sub.1-C.sub.6alkoxy, carbonyl, C.sub.1-C.sub.6alkoxycarbonyl; or R.sub.1 and R.sub.2 together with the adjacent --CO--N--CO-- group may form a monocyclic, bicyclic or polycyclic ring, said ring having up to 50 non hydrogen atoms and wherein said ring may contain the structural element (formula III) more than once; R.sub.3 if n is 1, is C.sub.1-C.sub.18alkyl, C.sub.6-C.sub.14aryl, aralkyl, C.sub.5-C.sub.12cycloalkyl, OR.sub.10 or SR.sub.11, NR.sub.12R.sub.13; wherein R.sub.3 if n is 2, is C.sub.2-C.sub.12alkylene, C.sub.6-C.sub.14arylene, xylylene R.sub.4 and R.sub.5, correspond to R.sub.1 and R.sub.2; R.sub.6 if n is 1, is hydrogen, C.sub.1-C.sub.18alkyl, C.sub.6-C.sub.14aryl, aralkyl, C.sub.5-C.sub.12cycloalkyl, NR.sub.14R.sub.15; wherein R.sub.6 if n is 2, is C.sub.2-C.sub.12alkylene, C.sub.6-C.sub.14arylene, xylylene; R.sub.7 is hydrogen, C.sub.1-C.sub.18alkyl, C.sub.6-C.sub.14aryl, aralkyl, C.sub.5-C.sub.12cycloalkyl, each of which may be substituted by halogen, C.sub.1-C.sub.4-alkyl, hydroxy, C.sub.1-C.sub.6alkoxy, carbonyl, C.sub.1-C.sub.6alkoxy-carbonyl; or R.sub.7 and R.sub.14 or R.sub.7 and R.sub.15 form together with the N-atom attached to R.sub.7 a 5-6 membered ring, optionally interrupted by --NH--, --N(C.sub.1-C.sub.8alkyl)-, --O-- and/or S-atoms. ##STR00001##