A positive resist composition contains a novolak resin in which 3-27 mol % of the hydroxyl group hydrogens are substituted with 1,2-naphthoquinonediazidosulfonyl ester groups, a methyl vinyl ether-monoalkyl maleate copolymer and optionally, an alkali-soluble cellulose whose glucose ring substituent groups are substituted with organic groups at a specific rate. The composition is useful as a thick film photoresist which is subject to a plating step and offers many advantages including high sensitivity, perpendicular geometry, high resolution, and crack resistance during and after the plating step.