A positive type photoresist composition comprises (a) a novolak resin and (b) a quinonediazide compound in wt. ratio of 1:1 to 6:1. The novolak resin is obtained by the addition condensation of a phenol and formaldehyde, in one stage by using as a catalyst an organic acid salt of a divalent metal more electropositive than hydrogen, or in two stages by using the acid catalyst in the subsequent stage, the phenol being at least one compound of formula:
wherein R is hydrogen or C1-4 alkyl group and being such that the average C number in the substituent per phenol nucleus is 0.5 to 1.5 and less than 50 mol% of the molecules have substituents at the ortho- or para-position with respect to the -OH group.
Preferred salts are acetates of Mg, Mn, Zn, Cd, Co, and Pb.
NMR spectra are shown of the resins.
The composition in solvent is coated on a support, and has a good resolving power.