This article explores the use of advertising and sponsored programming on Irish radio from its inception in 1926 until the arrival of Irish television in the 1960s. It discusses the financial dependence of 2RN (later Radio eireann) on advertising money and the ways this operated in tension with official concerns about that money's influence on programmes and audiences. There is a particular focus on the hugely popular radio soap opera The Kennedys of Castleross, which was sponsored by chocolate company Fry-Cadbury's and ran for 18 years from 1955. Using production archives, the article discusses the structures and economics of the programme, including the ways in which the sponsor and their advertising agency were directly involved in its writing. It also examines the ways in which, aside from the direct advertising for Cadbury products, The Kennedys of Castleross carried within its storylines values of the industrialisation, consumer culture and new economic models which were beginning to emerge in Ireland of the late 1950s. The discussion concludes by exploring the ways in which the arrival of television broadcasting in Ireland after 1961 changed the political economy of sponsored radio programming such as The Kennedys.