This study investigates the variations in behaviour displayed by young people who sexually harm, as previous research has shown that they are not a homogeneous sample. Three conceptually distinct sets of behaviour were hypothesized, relating to various modes of interaction between the young people with harmful sexual behaviour (HSB) and their victim, victim as object, victim as person and victim as vehicle. Thirty-three behaviours were drawn from an extensive review of the files of 300 youths who had sexually harmed. The pattern of co-occurrence of the presence or absence of these behaviours was revealed by a multidimensional scaling procedure, Smallest Space Analysis (SSA). The results provide empirical support for three distinct behavioural themes; 258 (86%) of the youths could be assigned to one dominant mode of interaction (victim as object, victim as person or victim as vehicle). The findings have implications for the ways in which practitioners differentiate between young people with HSB. (Contains 3 tables and 3 figures.)