Purpose – The range of prevalence of personality disorder (PD) found in people with intellectual disability (ID) has been reported as vast, and has included data from dissimilar settings. The purpose of this paper is to review the reported prevalence of PD in the general population of people with ID, and to consider how different and changing ideas about PD have affected these rates. Design/methodology/approach – Cross-sectional studies of the prevalence of PD in people with ID were identified. The quality of the studies was considered, along with how cases of PD were identified. Findings – Six studies were included. The reported prevalence of PD in people known to have ID ranged from 0.7 to 35 per cent. Possible reasons for this wide range included different views of PD and methods of assessment. Research limitations/implications – The wide range of findings suggests that methodological differences are significant. Consideration to how clinicians should respond to the overlap of impairment between ID and PD may improve the conceptual clarity of PD, informing future epidemiological research. Originality/value – This review was limited to studies of samples likely to be representative of the general ID population. The range of prevalence estimates was narrower than previously reported, and more likely to reflect the true prevalence rate of PD amongst people who have ID. Consideration was also given to how different ideas of PD led to different methods and may have contributed to variance in the results.