Researchers studying cognitive distortions of sex offenders have focused most of their efforts into developing psychometrically robust measures of dysfunctional beliefs and attitudes. In this paper research is discussed concerning four commonly accepted and widely used measures, and four recently developed instruments. We conclude that although some questionnaires are able to discriminate between the target group and control groups, several are open to social desirability bias. For only one scale, the Child Molest Scale, ability to discriminate between a target group not promised anonymity and a control group was reported. Although this instrument may announce a new step in the domain of assessment of cognitive distortions, it is argued that future tests should tap automatic processing in an attempt to avoid contamination by social desirability factors.