OBJECTIVES: Disease specific measures (DSM) and generic utility measures (GUM) both provide information about the health status of patients. Generally, a DSM tends to provide more descriptive information than a GUM but does not provide a utility. In order to get the best of both worlds, utility weights from a GUM might be linked to DSM health states in a mapping study. The appropriateness of such a mapping approach hinges on the comparability of the information captured by both types of instruments. The aim of this study was to assess the comparability of the information captured by a DSM and a GUM and the validity of obtaining utilities for the DSM via mapping. METHODS: We compared the Oxford Hip Score (OHS) and the EQ-5D in patients undergoing total hip replacement using data from the UK PROMs2 study. The comparability of the type of information was assessed using factor analysis and analysis of the correlation matrix. RESULTS: Comparing the instruments showed clear differences in the conceptualisation of the two measures. Factor analyses showed that the OHS data can be associated with 3 distinct constructs: one relating to pain, one to movement, one to daily activities. The 12 items of the OHS loaded on 4 of the 5 dimensions of EQ-5D (no OHS items loaded onto the “anxiety/depression” factor). Also, the results of the exploratory and confirmatory factor analyses describe systematically that -compared to EQ-5D- the OHS items are multidimensional by nature and that the same phenomenon is picked up repeatedly by different items. CONCLUSIONS: The differences we found between the two types of instruments do not impede the merits of either when used for their own purposes. However, the conceptual differences between the two types of instruments will have a major impact on the way utility values for a DSM are obtained via mapping.