This paper discusses the results of a study of the role of the computer in scaffolding pupils' interaction and its effects on the disabled (D) pupils' participation and inclusion in the context of socio-cultural theories and the ideals of inclusive education. The study investigated the interactions of pairs of D and non-disabled (ND) pupils working together on computer-based tasks, in mainstream primary schools in Cyprus. Twenty dyads of pupils (each comprising a D child and an ND peer) were observed and videotaped while working together at the computer. Data analyses were based on the collaborative nature of events for the non-verbal interaction and the functional-structural approaches for verbal interaction. Through application of video analyses, seven central aspects of interaction were identified: helping behaviours, motivation, self-confidence, peer-acceptance, affection, positive and negative socio-emotional status, and the input of the computer. Results of the study showed that the computer was a mediational scaffolding agent of the other six areas of the participants' interaction as it: (1) was an important interactional agent in initiating and terminating a conversation, (2) facilitated interaction and participation, as an intellectual and physical tool, (3) promoted different styles of interaction (not always positive ones) through the various input and output devices, by differentiating participation. Hence, the computer emerged as the third party in the collaborative activity which provided various opportunities and motivations for interaction.