Epoxidation of dicyclopentadiene (DCPD) is studied on a series of TiO2 catalysts using hydrogen peroxide as an oxidant. DCPD derivatives have applications in several areas including polymer, pharmaceutical and pesticide products. The control of selectivity leading to the desired product is important for many of these applications. Using experimental and computational studies, we show that the surface crystalline phases of TiO2 play crucial roles not only in the formation of peroxo species but also in the selective epoxidation of two different CC double bonds in DCPD.