A small group of children and young adolescent with dyslexia has severely impaired reading skills despite prolonged special education. These are the students in focus. In dyslexia, problem behaviour, internalised as well as externalised, has previously been reported, so also for the participants with dyslexia in this study. The aim of the present study was to obtain more in-depth knowledge of the behaviour problems from various informants, representing different settings. This kind of information is imperative for identifying problem behaviour, and for planning and implementing remedial programmes. A clinical group of 70 students with severe dyslexia, due to phonological problems, and a control group of 70 without reading problems participated. The two groups were pair-wise matched on age, gender, cognitive level and whether they lived in rural or urban areas. Mean age was 150 months, and mean IQ was approximately 100 in both groups. Parents, teachers and participants provided information on behaviour through the Achenbach questionnaires Child Behavior Checklist, Teacher's Report Form and Youth Self Report. Behaviour is, in these questionnaires, divided into eight syndrome areas called Withdrawn, Somatic Complaints, Anxious/Depressed, Social Problems, Thought Problems, Attention Problems, Delinquent Behavior and Aggressive Behavior. The three informant groups reported significantly more problems in the dyslexia group than in the controls in all the syndrome areas. Parents reported more children with dyslexia to be anxious and depressed, and have social problems and attention problems than teachers. They also reported suicidal ideations in nine participants with dyslexia. In addition, parents rated more internalising and total problems in the dyslexia group than teachers. (Contains 2 tables.)