On-field aggressive behaviour is often seen on sports fields and numerous theories tried to identify its origins. This study tackled the question of whether the youth athletes in contact and non-contact sports could be differentiated on the basis of the hostile and competitive aggression, and some other characteristics that showed to be related to the aggressive onfield behaviour. The study sample comprised 154 of (51% girls) young athletes aged between 10 and 15 years from various contact and non-contact disciplines (wrestling, boxing, taekwondo, football, swimming, athletics, and dance). Participants completed several questionnaires regarding their aggressive behaviour, motivation, anxiety, self-esteem and emotional regulation. Only the competitive, but not hostile, aggression was more present among the youth athletes in contact sports. From all other characteristics, self-esteem, although in a lower extent, predicted affiliation of the non-contact sports group.