Background ‘No‐show’ is important in today's mental healthcare services, yet in forensic psychiatry, little is known about its relationship to general and disorder‐specific patient characteristics. Aims The aim of this article is to determine the prevalence of no‐show and any general and disorder‐specific features associated with no‐show in a cohort of offenders with attention deficit hyperactivity disorder registered at a specialist forensic mental health clinic. Methods Participants were 118 adult men with a mean age just over 32 years (SD 8.75) attending forensic mental health outpatient clinics in the Netherlands who had a primary diagnosis of attention deficit hyperactivity disorder and who had been aggressive and/or delinquent. Results Over a 1‐year period, most patients (101, 86%) missed at least one appointment. The average number of appointments offered was 37.88 (SD = 27.27), and the average number of no‐shows was 6.53 (SD = 5.99) per patient. Multivariate linear regressions showed a 10‐fold likelihood of later no‐shows if the first appointment was missed; not showing up after the intake procedure was also associated with higher rates of later no‐show. None of the disorder‐specific characteristics contributed to the problem. Conclusions No‐show is of particular concern in forensic mental health settings. In the current study, no‐show was primarily associated with features related to the time of initial consultation. More attention should thus be paid at this stage to using a standard method of assessing a wider range of variables likely to affect attendance. Copyright © 2016 John Wiley & Sons, Ltd.