Following advances in overall management and improved outcomes, an increasing number of adolescents with cardiac disease are reaching adult age. Patients in general, including adolescents, seem to have a poor knowledge of their illness, which may further reflect in a less optimal quality of life. As a guide to their knowledge of their cardiac condition, adolescents were asked to draw a diagram of their cardiac abnormality. Relatively well adolescents aged 12–20 years with a cardiac abnormality were consecutively recruited from an ambulatory setting. All were asked to draw a picture of their cardiac abnormality and describe their condition. A total of 120 patients were recruited and had conditions varying from a hyperplastic right ventricle to a small ventricular septal defect. Only 60 (50%) of the patients completed a drawing, of which one-third did so at the time of attendance. Nevertheless, there was no difference between the accuracy of the adolescents’ drawings completed at home or at the clinic. Only three patients drew an accurate diagram of their congenital cardiac abnormality. A further nine patients drew a reasonably correct diagram, 13 patients a partially correct diagram, whereas 35 patients submitted incorrect diagrams. Adolescents with congenital cardiac disease, many having been cared for since infancy with regular cardiological reviews, had a poor anatomical knowledge of their cardiac lesion, as reflected by their inability to correctly draw their abnormality. These findings suggest the need for improved strategies in developing appropriate education programmes for this patient population.