PURPOSE: To obtain a composition improved in light resistance excellent in heat and impact resistances by mixing a polyphenylene ether resin with a specified compound in a specified mixing ratio.

CONSTITUTION: The composition comprises 100 pts.wt. polyphenylene ether resin or mixture thereof with a styrene resin [e.g. poly(2,6-dimethyl-1,4-phenylene) ether] and 0.01-5 pts.wt. compound of the formula: R-AnBn'-R' {wherein A is a bivalent group of formula I, B is a bivalent group of formula II [wherein R1 and R2 are each H, 1-12C alkyl or aryl; R, R' and R3 to R5 are each H, 1-8C alkyl aryl or aralkyl with 1-8C alkyl, or any two of them together with an oxygen atom may form a siloxane ring; X is -CmH2m-C(=O)O (wherein m is 1-3); Y is a single bond when A is bonded to R, or is O in the other cases; n is 1 or greater; n' is 0 or greater; As and Bs may be bonded to each other to form blocks or may be bonded randomly]}.