There is disclosed a resist composition which shows high sensitivity and high resolution on exposure to high energy beam, provides reduced Line Edge Roughness because swelling at the time of development is reduced, provides minor amounts of residue after development, has excellent dry etching resistance, and can also be used suitably for the liquid immersion lithography; and a patterning process using the resist composition. There can be provided a resist composition which comprises, at least, a polymer including repeating units represented by the following general formulae (a) and (b).