There is a continuing debate on the etiology and development of pedophilia, i.e. sexual interest in prepubertal children. Though experts have diverging concepts regarding the main etiological factors, it is often described to root in adolescence. However, the empirical basis for understanding its development is poor. The Hamburg Youth project aims at exploring paraphilic developments in adolescents with a focus on the development of possible pedophilic interest. The project strives for a better understanding of the development of different dimensions of sexual interest especially in male adolescents by investigating how their sexual phantasies and behaviors progress, aiming at finding a basis for better treatment strategies during this crucial developmental period. We present the background, framework, therapeutic approach and the goals for this project starting in 2018. The project offers anonymous counselling, a diagnostic process and if necessary therapy. It addresses adolescents between 12 and 18 years. The therapeutic concept involves a biopsychosocial understanding of psychosexual development and an integrative family-centered approach. Next to the single sessions, parental and family sessions take place regularly. The basic assumption is that in adolescence there is still great potential for development for the participants, also with regard to their sexual interests.