This paper presents an account of a major research study conducted at the end of 1987 on behalf of Capital Radio pic. Capital Radio is a major independent radio station broadcasting in London and its immediate environs. This study was designed with the aim of quantifying the differences between radio and television in terms of the immediate impact of commercials broadcast. Thus the specific brief was to produce comparative measures of the recall of advertising on Capital Radio and the major commercial TV Stations operating in the London area. The paper covers the background to the study, an account of the data collection and analysis procedures used, and a summary of the results. It aims to take the discussion of the potential of the two media beyond presence, and into the realm of the effectiveness of their power to communicate with their audience.