This review describes the incidence of posttraumatic stress disorder (PTSD) in physically ill patients. At the beginning, research in the field of PTSD was primarily focused on war veterans and victims of bodily assault or rape. Starting in the early 90 s, PTSD after civilian traumas such as motor vehicle accidents was diagnosed increasingly more often. Recent publications showed that PTSD can also follow serious somatic diseases. Hence, awareness during anaesthesia, prolonged ICU treatment (ARDS, septic shock), burns, successful resuscitation after cardiac arrest, coronary artery bypass surgery, organ transplantation and cancer were all linked to the development of PTSD. Prevalence of PTSD in these medical conditions lies around 5 - 10 %, and it is therefore considered an important comorbidity. Unfortunately, the diagnosis and treatment of PTSD are not well enough established yet and thus do receive too little attention in the treatment regime of somatic illness. Generally, PTSD can occur with every life-threatening disease, but possibly also with less severe diseases if the patient experiences intense fear. PTSD symptoms, especially intrusive recollections, avoidance and hyper-arousal can impair the patients' quality of life more than the primary disease. This seems to be also true for sub-syndromal PTSD. To adequately diagnose and treat patients at risk of developing PTSD, close collaboration between physicians of all subspecialties and psychiatrists will be necessary.