The Children's Communication Checklist (CCC) was developed to provide an objective assessment of pragmatic aspects of children's communication difficulties. We aimed to (1) see whether the checklist provided valid and reliable information when completed by parents, and (2) consider its usefulness in a clinical context. Checklists were completed by parents and a professional who knew the child well for all 5 to 17-year-old referrals to a tertiary developmental paediatrics centre over a 31-month period. Children who were not yet speaking in sentences were excluded. From a sample of 151 children (81% male; mean age 8.7 years) with pervasive or specific developmental disorders, valid checklists were completed by 119 parents and 93 professionals. Reliability, as measured by internal consistency, was 0.7 or higher for most scales. Correlations between ratings for parents and professionals were in the range of 0.30 to 0.58 for individual pragmatic scales, with a correlation of 0.46 (n=82) for the pragmatic composite. For both parents and professionals, the pragmatic composite was lowest for children with a diagnosis of autism; intermediate for those with a diagnosis of Asperger syndrome, pervasive developmental disorder not otherwise specified or attention-deficit–hyperactivity disorder (ADHD); and highest for those with a diagnosis of specific learning disability. The strongest relation between the pragmatic composite and diagnosis was seen when ratings from parents and professionals were combined. Differences between diagnostic groups were not explicable in terms of age or verbal IQ.