Patients after spinal cord injury, severe brain trauma and cerebral stroke (ischemic or hemorrhagic) are often immobilized in bed or wheelchair for months or even years. One of the main risk factor for deep vein thrombosis is just prolonged immobilization.The aim of the study was to evaluate the frequency of symptomatic and asymptomatic thrombosis among immobilized patients because of severe brain damage and spinal cord injury.Material and methods. The study included 59 patients with tetra or paraparesis after severe brain damage or spinal cord injury, hospitalized in the University Hospital in Bydgoszcz in the Department of Rehabilitation over the period 2007-2008. All of them had lower extremities duplex-scan ultrasound as a screening examination and D-dimer testing.Results. Thrombosis was confirmed in nine patients (15% of all examined) and two patients (23%) in his group were of asymptomatic. 77% of diagnosed patients had only low extremities edema. Full symptomatic thrombosis with low extremities edema, increased warmness and redness were observed in 22% of patients.Conclusions. It is advisable to make periodical lower extremities venous system examination to exclude deep vein thrombosis. The risk of missed diagnosis in this group of patients is connected with increased percentage of embolism complications during the rehabilitation process. In patients after spinal cord injury, there are indications to examine the patients' venous system periodically.