[Problem] Provided is a resin having an alicyclic structure in a main chain, which is excellent in etching resistance and developing property, a resist composition for exposure with a high energy radiation using the resin, and a method for forming a pattern using the resist composition. [Means to Solve] Also provided is a hydrogenated ring-opening metathesis polymer which is comprised of alicyclic skeleton-containing structural units [A], [B] and a structural unit [C] selected from the following general formula [5] and/or [6]: wherein, e and f represent respectively an integer of 0 to 3, wherein the at least one of X1 of the general formula [1] of the structural unit [A], X of the general formula [3] and X3 of the general formula [4] of the structural unit [B] is —O—, and wherein the molar ratio of the structural units [A], [B] and [C] satisfies simultaneously that [A]/([B]+[C]) is from 20/80 to 98/2, ([A]+[B])/[C] is from 99/1 to 50/50, and ([A]+[C])/[B] is from 99/1 to 21/79. Also, a resist composition comprising the same and a method for forming a pattern are provided.