In this review, we provide an overview of the risk factors for venous thromboembolism, focusing on hypercoagulability and hypofibrinolysis. In the first part of this review, we discuss the risk factors for commonly occurring venous thrombosis, in particular deep vein thrombosis and pulmonary embolism. In the second part, we provide an overview of the risk factors for the Budd-Chiari syndrome and portal vein thrombosis. These are rare, life-threatening forms of venous thromboembolism located in the splanchnic veins. There are many similarities in the risk profiles of patients with common venous thrombosis and splanchnic vein thrombosis. Inherited thrombophilia and hypofibrinolysis increase the risk of both common venous thrombosis and splanchnic vein thrombosis. However, there are also apparent differences. Myeloproliferative neoplasms and paroxysmal nocturnal hemoglobinuria have a remarkably high frequency in patients with thrombosis at these unusual sites but are rarely seen in patients with common venous thrombosis. There are also clear differences in the underlying risk factors for Budd-Chiari syndrome and for portal vein thrombosis, suggesting site specificity of thrombosis even within the splanchnic venous system. These clear differences in underlying risk factors provide leads for further research on the site specificity of venous thrombosis and the development of thrombosis at these distinct sites.