2-Adamantanone was selectively produced by photocatalytic oxidation of adamantane in acetic acid using TiO2 powders. The reactions were carried out at ambient and acetic acid reflux temperatures with and without an oxidant. Adding oxidant in refluxing acetic acid under irradiation remarkably increased conversion and selectivity. Rutile TiO2 powders showed better conversion and selectivity in the presence of H2O2. The total conversion was 67% and the highest selectivity of 2-adamantanone was 89%.