Aims: This thesis investigates the socio-emotional functioning of children with Specific Language Impairment. It aims to: i) investigate different types of behavioural, emotional and social difficulties; ii) examine which language dimension (receptive vs expressive vs pragmatic language ability) is related to difficulties with socio-emotional functioning; iii) explore the role of social cognition; iv) examine whether the nature of children's difficulties are context specific. Sample: Participants were forty-two children with SLI, forty-two children matched for chronological age and non-verbal cognitive ability, and forty-two children matched for language ability. The children were identified from five mainstream primary schools and one Language Unit. Method: Parents and teachers completed a behavioural questionnaire assessing socioemotional functioning, and a communication checklist assessing pragmatic language ability. The children were assessed on tasks measuring emotion identification, emotion labelling, emotion explanation, and knowledge of conflict resolution strategies. Results: The SLI Group was rated significantly higher by parents and teachers than both matched groups on all the Strengths and Difficulties Questionnaire subscales indicating considerable problems with socio-emotional functioning. Parents and teachers reported increased difficulties in children's pragmatic language ability on Children's Communication Checklist-2 and varying significantly to both matched groups. Significant variations between parent and teacher reports on difficulties with socio-emotional functioning and pragmatic language ability existed only for the SLI Group. Significant group differences were found for all the social cognition tasks. Social cognition, but not language ability, predicted both parent and teacher rated behavioural, emotional and social difficulties for the SLI Group. Conclusions: The results challenge current understanding about difficulties with socioemotional functioning experienced by children with SLI by pointing to the crucial role of social cognition and the importance of the social environment. Atypical developmental trajectories are evident for this group of children with factors other than language playing more of a role for their socio-emotional functioning.