Numerous studies have identified risk factors for acute and long term posttraumatic symptoms following traumatic exposure. However, little is known about possible common pathways to the development of acute stress disorder (ASD) and posttraumatic stress disorder (PTSD). Research suggests that a common pathway to ASD and PTSD may lie in peritraumatic responses and cognitions. Using structural equation modeling we examined the role of three peritraumatic factors (tonic immobility, panic and dissociation) and three cognitive factors (anxiety sensitivity, negative cognitions about the world, and negative cognitions about self ) on the development of ASD and PTSD severity in a national study of Danish bank robbery victims (N = 450). Peritraumatic panic, anxiety sensitivity, and negative cognitions about self were found to be significant common risk factors, whereas peritraumatic dissociation was only a significant risk factor of ASD severity. Together with two control factors these factors explained 73 % of the variance in ASD severity and 52 % of the variance in PTSD severity. Future research should focus on replicating these results across different trauma populations as they point to possible areas of preventive and treatment actions to be taken against the development of acute and eventually long-term posttraumatic stress symptoms.