Background: Speculation on the role of cognition features heavily in most theories of childhood sexual abuse (CSA). However the focus of empirical research has mainly been on surface level cognitions. This research attempts to examine the processes occurring at the information processing level of cognition in two groups of sex offenders (a pre-treatment group and a post-treatment group) and a non-sex offenders control group. The three groups were compared on performance in an attentional bias task and a cognitions questionnaire. It was expected that the sex offenders waiting for treatment will have an attentional bias towards images of children and that those who have completed treatment will show less of a bias. The non-sex offenders were expected to have an attentional bias towards adult sexual images. Performance on the questionnaire was expected to mirror performance in the attentional bias task. Method: 95 participants were recruited for this study: 32 in the pre-treatment group, 32 in the post-treatment group and 31 non-sex offenders. Participants were all recruited from UK prisons. All participants completed both tasks. Results: Performance on the attentional bias tasks did not support the hypothesesthat is, the groups did not differ in how they processed the various images. In contrast the groups differed in performance on the questionnaire. The pre groups endorsed more CSA supportive cognitions than the post and non-sex offender. The post group and non-sex offenders did not differ on the questionnaire. Discussion: It is proposed that the lack of support for some of the original hypotheses may be due to a tendency for participants to respond in a socially desirable manner. It is also proposed that some subgroups of offenders may have been underrepresented in the sample. Suggestions are made for possible directions of future research