An innovative methodology is presented for describing the therapeutic processes involved in five types of adolescent treatments: psychoanalysis, psychodynamic psychotherapy, cognitive-behavioural therapy, mentalisation-based treatment and interpersonal psychotherapy. Using the "Adolescent Psychotherapy Q-Set" (APQ), 18 experienced clinicians representing these different orientations were asked to rate their "actual" and "typical" practice as well as give feedback on the quality of the initial face validity of the APQ items. The results suggested that this new measure can be considered a meaningful tool for describing the adolescent psychotherapy process, and that it can help us identify some interesting patterns relating to it, as well as certain similarities and differences between different therapeutic approaches. (Contains 6 tables.)