Two spent activated C samples formerly used as Zn(OAc)(2) catalyst support or water treatment sorbent were regenerated by oxidn. with H(2)O(2) or CaO(2) in aq. medium at pH 3 and room temp. The activated C used as a catalyst carrier recovered its porous structure, sorptive capacity and activity after the regeneration, while the water treatment sorbent could not be sufficiently regenerated in the Fenton reaction. Use of CaO(2) was as efficient as H(2)O(2) but contributed to an improvement of the chem. nature of the activated C surface.