Mental imagery is increasingly considered to be an important feature in anxiety disorders. The aim of this study was to investigate the prevalence and characteristics of mental images in obsessive compulsive disorder (OCD) and their possible association with earlier adverse events. A consecutive sample of 37 patients with OCD admitted to a specialist unit was interviewed using a semi-structured interview. Thirty (81%) patients with OCD reported mental images. Most images were either memories of earlier adverse events (n=10 or 34%) or were associated with them (n=13 or 45%). Patients with mental images had more obsessive compulsive symptoms, responsibility beliefs and anxiety than those without. Previous research has shown that patients with OCD and comorbid posttraumatic stress disorder might not benefit as much from standard behavioural treatment as those without. Consequently, additional therapeutic interventions such as imaginal reliving and restructuring of meaning or imagery modification of traumatic memories might be helpful in OCD patients with mental images that are linked to earlier adverse events.