Preference representation and reasoning is a key issue in many real-world scenarios. Currently, there are many approaches allowing preferences to be assessed in a qualitative or quantitative way. The most prominent qualitative approach for representing preferences are CP-nets. Their clear graphical structure unifies an easy representation of user desires with nice computational properties when computing the best outcome. Here, we introduce ontological CP-nets, which allow the representation of preferences using a CP-net over an ontological domain, i.e., variable values are logical formulas constrained relative to a background domain ontology.