Abstract The cabinets of the European Commission are seen to play a crucial role in the policy-making process. So far, however, they have in many respects remained black boxes. In this article we unpack the demographic composition in terms of nationality of three commissions' cabinets. The standard portrayal of cabinets has been that of national enclaves and points of access. Reforms during the period have required a more multinational composition. Our study shows that not only have the new rules been implemented: the new formal requirements have become over-fulfilled and increasingly so. In 2004, 96 per cent of the cabinets contained more nationalities than formally prescribed and 57 per cent of the personnel were non-compatriots of their respective commissioners. Based on studies of comparable phenomena, it is reason to believe that decomposition of a particular demographical cluster within an organizational unit reduces the impact of such demographical factors on officials' decision behaviour.