This study examined the language, achievement, and cognitive characteristics of 380 children, aged 7 to 14 years, consecutively referred to child psychiatric services. Among those children referred solely for psychiatric problems, 40% had a language impairment that had never been suspected. Children with previously identified and unsuspected language impairments were similar with respect to receptive and expressive language and on measures of cognitive processing. Although both groups of children with language impairments exhibited poorer academic achievement than children with normal language, children with previously identified language impairments had the lowest achievement. The milder achievement problems of children with unsuspected language impairment may explain why their problems had not been suspected. Both the clinical and theoretical implications of the findings are discussed. Heightened awareness concerning the high frequency of language impairment and other cognitive processing problems in children referred for psychiatric assessment and treatment should lead to more systematic examination of language functioning and evaluation of the impact of language and communication functioning on therapeutic outcomes.