Digital advertising, both display advertising and search advertising, represents a very important part of the overall advertising market in the United Kingdom. Google and Facebook have a high degree of market power in search and display advertising, respectively. On 1 July 2020, the Competition and Markets Authority published its Final Report on its market study into online platforms and digital advertising, in which it looked in some depth at digital advertising markets, assessing whether a lack of transparency, conflicts of interest, and the leveraging of market power undermine competition in digital advertising. This article examines the issues considered by, and the findings of, the CMA in its Market Study and set out in its Final Report, and describes the policy options identified in the Market Study for promoting competition and other policy goals, such as data protection and privacy and ensuring the viability of news publishers, in digital advertising markets.