Troublesome behaviours of adolescent patients are explained using the cognitive-developmental framework of Elkind (1978). Self-contradictory and seemingly irrational behaviours reflect the limited experience of adolescents with newly acquired thinking and reasoning processes. The most important task of adolescence is establishing the adult identity. Just as physiological factors are producing a new adult body, cognitive processes are producing a new adult mind with new behaviour patterns. The erratic behaviours of adolescents are 'symptoms' of the cognitive-developmental process. Four such symptoms are described. 'Pseudostupidity' is the adolescent's tendency to overlook the obvious and inability to make appropriate choices. It results from the lack of experience with newly attained abilities to perceive many possibilities simultaneously. The 'imaginary audience' is the adolescent's self-conscious belief that everyone is watching and evaluating him or her. It reflects the new ability to think about the thoughts of others and the inability to distinguish them from personal thoughts. The 'personal fable' refers to a strong feeling of invulnerability and uniqueness, which reflects an incomplete understanding of the self. 'Apparent hypocrisy' comes from the new ability to conceive ideals and the inability to relate ideals to behaviours. These constructs are applied to situations in the dental setting that reflect difficulties in communication between dentists and adolescent patients and the aesthetic concerns of adolescents. Dentists are advised to remember that adolescent behaviour patterns are not fixed. Of primary importance is the willingness of dentists to listen to young patients and to work towards trusting relationships with them. By serving as a stable adult role model the dentist can facilitate the adolescent's personal growth, as well as positively influencing dental health.