Objective: The objective of this study was to assess whether adults with ADHD in a forensic sample had received the

diagnosis earlier and to investigate reasons for missing the diagnosis earlier. Method: From December 1, 2007 until March 5,

2009, all patients from an outpatient clinic for forensic mental health care who were suspected of having ADHD were seen

by a psychiatrist who assessed presence and severity of ADHD symptoms and other psychiatric disorders in a standardized

way. Results: ADHD diagnosis was missed previously in life in 59 of 106 male adults (56%). ADHD diagnosis was missed

more often in older men, in those with hyperactive/impulsive or combined subtype of ADHD, in those who reported fewer

symptoms of ADHD in childhood or adolescence, in those with a comorbid mood disorder in adulthood, and in those who

had never received mental health care before. Even in those who had previously received mental health care, the diagnosis

had been missed in 42% of the cases. Prior contacts with police or court also predicted missing the diagnosis, an effect that

was mediated by a lower chance to be referred to mental health care. Conclusion: General and forensic mental health care

workers should be alert for the fact that ADHD is missed very often in individuals who have problems with delinquency

and should realize that ADHD may be masked by various factors. (J. of Att. Dis. 2012; XX(X) 1-XX)