The authors analyse specific features of post-thrombotic syndrome in 98 patients aged between 26 and 80 (mean 58.6) years during the follow up period after the implantation of the cava filter. The patients (80 (81.5%) men and 18 (18.4%) women) were divided into two groups. Group 1 was comprised of 31 (31.6) patients presenting with inferior vena cava occlusion at the level of the cava filter. Group 2 included 67 (68.4%) patients having the inferior vena cava with the unobstructed lumen and the normally functioning cava filters. The results of the study indicate that the majority of the patients in group 1 eventually developed post-thrombotic syndrome at different periods after the implantation of the cava filter whereas this pathology occurred only in a few patients of group 2.