In this article we examine the effectiveness of a new format of interactive advertising with respect to the user's interest and preference for a product while watching a TV programme of relative importance. More specifically, our objective was to test a new ad format for interactive digital television in comparison to an established one, and to examine how the differences in the programme flow and in the degree of user attendance would affect his or her preferences and satisfaction. The design of ads was based on Adobe Director and a usability evaluation was conducted, before the production of the ad prototypes for the research on their effectiveness. Additionally, the technical limitations of current business practice and the European legal framework for the audio-visual interactive media environment have been taken into consideration, in order to provide a feasible and applicable system. Empirical findings suggest that the new ad format (Selectable Item Ad -SIA) is highly effective for people's interest and participation. Our research provides insight for advertisers and producers, because it establishes that the design of a suitable ad depends