Previous studies using a primary task procedure have demonstrated that an experimental pain stimulus interrupts ongoing task performance in healthy volunteers and patients, and that this interruption is intensified by catastrophic thinking about pain and the perceived threat value of the pain stimulus. However, no studies have investigated the interruption of attention by relevant threatening stimuli in specific patient samples. In the present study, 40 patients with chronic whiplash syndrome and 40 healthy controls performed a primary task while simultaneously a potentially threatening neck fixation (i.e., extension and rotation) was imposed. Pain catastrophizing, fear of movement/(re)injury, hypervigilance, and depression were assessed. The patients showed a more pronounced deterioration of performance compared to controls when the neck rotation and extension fixations were introduced. Within the groups, neither catastrophic thinking nor fear predicted the magnitude of the performance deterioration.