To date, in publications on hamartomas, precocious puberty and laughing seizures have been discussed, but behavioural and cognitive abnormalities have been neglected. Therefore, we report a 14-year-old girl with a proven hamartoma, in which abnormalities of behaviour and cognition played an important role within the somatopsychic complex. In our patient, urinary incontinence during the seizures and psychiatric symptoms, such as eating disorder with obesity, school phobia, antisocial behaviour, withdrawal and cognitive problems (e.g. general slowness, deficiency of cognitive flexibility) came to the fore. The girl had not attended school regularly for almost 2 years, had stayed at home and was overtaxed psychosocially. The seizures and the urinary incontinence improved with drug treatment, but psychiatric difficulties increased and remained untreated until the girl came to a child psychiatric inpatient clinic where drug treatment and behavioural therapy were combined. During well-coordinated neurological and psychiatric treatment the laughing seizures (spontaneous, event-related, psychogenic) decreased and a considerable improvement in psychiatric and psychosocial problems was attained. Consequently, we recommend a close and timely integration of the psychiatric aspects in the treatment of children with hamartomas.