A polymer comprising recurring units of formulae (1) to (4) wherein R.sup.1, R.sup.3, R.sup.4 and R.sup.7 are hydrogen or methyl, R.sup.2 is an acid labile group, R.sup.5 and R.sup.6 are hydrogen or hydroxyl, and R.sup.8 is a lactone structure group and having a Mw of 1,000-50,000 is provided. A resist composition comprising the inventive polymer has a sensitivity to high-energy radiation, improved resolution and etching resistance and lends itself to lithographic micropatterning with electron beams or deep UV. ##STR00001##