The different cognitive beliefs about offending exhibited by offenders are discussed. The question addressed in this paper concerns the extent to which beliefs and social knowledge about offending differentiate between different characteristic types of offending (drug abuse, theft, sexual and violent). Two hundred and ninety adult male prisoners in four Taiwanese prisons provided selfreported criminal histories. From these a crime index indicative of the proportion of offences of each type (or specialism in offending) was calculated for each offender. Offenders legitimize their own offending while they tend to regard the offences of others negatively. In this way, cognitive representations may reinforce an offender's specific pattern of criminal acts while also insulating them from pressures towards other criminal activities. Evidence is presented that offenders' social knowledge development is consolidated around crime themes.