Ubiquitous collaborative systems are difficult to design; particularly those where the participants are human beings and there is not a pre-established workflow to coordinate the activities conducted by them. A key challenge for designers of these systems is to envision and represent scenarios where the interaction among users can take place, and thus provide appropriate services to the supporting application. A few modeling languages and notations have been proposed for specifying interaction scenarios among users, but none of them has been broadly adopted by systems’ designers, probably because there is not clear evidence that helps engineers decide what notation to use. This paper reviews the three main visual notations proposed to model computer-mediated interaction scenarios and presents an experimental study that analyses not only the usability and usefulness of these notations, but also the tensions among these aspects. The study results help designers identify suitable user interaction representations to support the requirement elicitation and analysis during the development of ubiquitous collaborative systems. The results can also be used to improve the usability and usefulness of other visual notations, and the relationship between these two aspects. In this sense, designers of modeling languages can take advantage of the study findings to generate new proposals or improve the existing ones.