Paedophilia is distinguished from incest. The classification of paedophilia into ‘Invariant’ and ‘Pseudo-Neurotic’ types is made and clinically illustrated. Some features of the psychopathological structure which paedophilia has in common with other perversions are described and the paper goes on to consider the influences these features have on the paedophiles’ internal and external object-relating and their detrimental effects on the paedophiles’ formative psychic processes and consequent character structure.