This thesis investigates the different attentional mechanisms involved when using ambient information systems. To that end, it defines and delimits pervasive computing – when computational resources are embedded into the environment and in everyday objects – and discusses the consequences of this technology, regarding the social impacts, environmental implications, security and privacy issues, highlighting the role of design on this matter. It presents the evolution of interaction design, emphasizing its relationship with the design of interactive media. It proposes to broaden the interaction design field, considering that the computer screen is no longer the primary interface with the digital environment, and that interaction design requires a systemic approach in the context of pervasive computing. It introduces Weiser and Brown s (1996) concept of calm technology, and deepens the discussion initiated by these authors about the need for designing information systems that act on the periphery of our attention, based on Cognitive psychology studies about attentional mechanisms. It highlights ambient information systems as those which have more properly embraced the idea of presenting information without requiring the focus of our attention. It analyzes twelve ambient information systems, investigating how the attentional mechanisms are involved in their usage. It concludes that Weiser and Brown s (1996) original concept is not sufficient to describe the myriad of processes involved with our attention, and outlines guidelines for the design of ambient information systems, in order to consider the dynamics between different attentional mechanisms, the context of use, the degree of user engagement, the influence of memory and the ability to habituate to information systems.