In patients with type 1 diabetes mellitus (T1DM), cardiovascular complications are the solid causes of morbidity. It is thought that there might be alterations of the coagulation system like fibrin clot structure, changes in procoagulant molecules concentration and reduction of the fibrinolytic system activity in patients with T1DM. However, the informations on coagulation disorders and altered fibrinolysis are lacking in children with T1DM. The associations between hyperfibrinogenemia and coronary artery disease or the development and activation of the atheromatous plaque has been reported. A clear association has been observed between the increase in plasminogen activator inhibitor-1 plasma levels and prothrombotic diseases such as hypertension, obesity, insulin resistance, and diabetes. Willebrand factor antigen has been proposed as a prognostic marker of metabolic and cardiovascular diseases, such as diabetes, myocardial infarction or stroke.