The current study examines significant variations in criminal achievement across sex offenders. To examine the “successful” sex offender, the study proposes a concept of achievement in sexual offending defined as the ability to maximise the payoffs of a crime opportunity while minimizing the costs. The study is based on a sample of convicted adult male sex offenders using retrospective longitudinal data. The study findings show a wide variation in criminal achievement, a variation that is not correlated with the severity of sentences meted out or the actuarial risk scores obtained by these offenders. Those offenders who specialize in sex crimes were shown to be the most productive and least detected offenders. Two types of successful offenders emerge, the first relying on his conventional background in targeting a victim that can be repeatedly abused for a long period without detection. The second is a younger offender that is successful in the sense of being able to complete aggressions on multiple victims. Results suggest that the successful sex offender is not “detected” once he enters the criminal justice system, nor is he handled in a way that may deter him from sexually reoffending in the future.