There has been significant research interest over recent years in the use of public digital displays and in particular their capability to offer both interactivity and personalized content. Although a number of interaction technologies have been investigated, a promising approach has been the use of the ubiquitous cell phone, which not only offers a means to interact with displays but increasingly offers a small but high-quality screen to complement the larger public display. However, to date there has been little investigation into the impact on users when interfaces are distributed across this type of dual screen setup. This article reports on a series of experiments carried out to determine if there is a significant quantitative or qualitative effect on user performance when interaction is split across large public and smaller private screens.