In Germany certain quantities of spent MOX fuel will be disposed in a rock salt repository. In order to assess the safety of the repository the corrosion behavior of spent MOX fuel in salt solution must be understood. Since material properties of spent MOX fuel are different compared to these of spent LWR UO2 fuel, it is not possible to deduce from corrosion behavior of the latter to that one of spent MOX fuel. It is expected that the most significant differences will occur in the dissolution kinetics, whereas similar solid alteration products are expected from the similar overall composition of the fuels. Various experiments were performed focused on the effect of fuel type on the dissolution kinetics. The results of this work are summarized and evaluated