This paper discusses data issues related to one of the key instruments of EU dairy policy, namely the national production quotas. More specifically, the paper demonstrates the importance of initial assumptions and estimates of quota rents when analysing EU dairy policy. In addition to the consideration of the overall size of the quota rent, the analysis also demonstrates the importance of recognising that the EU dairy regime consists of national quotas – not an EU-wide quota. Hence it is the underlying relative competitiveness of EU milk producers at the national level that determines the size of the quota rents being earned in the individual EU countries. The paper highlights the need for further data work in order to be able to analyse EU dairy policy, including a survey to establish new estimates of national quota rents and an effort to disaggregate the single dairy sector in the standard GTAP database.