Chemically amplified photoresist compositions comprising, (a) a compound which cures upon the action of an acid or a compound whose solubility is increased upon the action of an acid; and (b) a compound of the formula (Ia), (Ib), (IIa), (IIb), (IIIa), (IIIb), (Iva), (Ivb), (Va), (Vb) or (VIa), wherein n is 1 or 2; m is 0 or 1; X.sub.0 is --[CH.sub.2].sub.h--X or --CH.dbd.CH.sub.2; h is 2, 3, 4, 5 or 6; R.sub.1 when n is 1, is for example optionally substituted phenyl, naphthyl, anthracyl, phenanthryl, or heteroaryl; R.sub.1, when n is 2, is for example optionally substituted phenylene or naphthylene; R.sub.2 for example has one of the meanings of R.sub.1; X is for example --OR.sub.20, --NR.sub.21R.sub.22, --SR.sub.23; X' is -X.sub.1-A.sub.3-X.sub.2-; X.sub.1 and X.sub.2 are for example --O--, --S-- or a direct bond; A.sub.3 is e.g. phenylene; R.sub.3 has for example one of the meanings given for R.sub.1; R.sub.4 has for example one of the meaning given for R.sub.2; R.sub.5 and R.sub.6 e.g. are hydrogen; G i.a. is --S-- or --O--; R.sub.7 when n is 1, e.g. is phenyl, optionally substituted, when n is 2, is for example phenylene; R.sub.8 and R.sub.9 e.g. are C.sub.1-C.sub.18alkyl; R.sub.10 has one of the meanings given for R.sub.7; R.sub.11 i.a. is C.sub.1-C.sub.18alkyl; R.sub.12, R.sub.13, R.sub.14, R.sub.15 R.sub.16, R.sub.17 and R.sub.18 for example are hydrogen or C.sub.1-C.sub.18alkyl; R.sub.20, R.sub.21, R.sub.22 and R.sub.23 i.a are phenyl or C.sub.1-C.sub.18alkyl; give high resolution with good resist profile ##STR00001## ##STR00002##