Pulmonary hypertension (PH) is a severe haemodynamic disorder in which the pulmonary artery pressure is persistently elevated, leading to right-sided heart failure and death. Recently, chronic myeloproliferative diseases associated with pulmonary hypertension were included in the group 5 category, corresponding to PH for which the aetiology is unclear and/or multifactorial. In this review we will describe the distinct forms of PH in the context of the myeloproliferative diseases chronic thromboembolic pulmonary hypertension and pre-capillary PH mimicking pulmonary arterial hypertension. The epidemiology, mechanisms and treatment approaches will be discussed.