To assess the histological bases of lymphadenomegaly, which has been reported as a frequent radiological finding in pulmonary veno-occlusive disease (PVOD), we have reviewed pulmonary and mediastinal lymph nodes resected during lung transplantations in 19 patients suffering from PVOD and related pulmonary capillary haemangiomatosis (PCH). Lymphatic congestion was common and was often obvious in subsegmental and segmental lymph nodes. Vascular transformation of the sinuses, intra-sinusal haemorrhage with erythrophagocytosis and lymphoid follicular hyperplasia were frequent especially in lobar, hilar and mediastinal lymph nodes. These lesions were very significantly less frequent in 33 cases of pulmonary hypertension unrelated to PVOD. Due to their thoracic location, these non-specific lesions could simulate other diagnoses such as Castleman disease or lymphangioleiomyomatosis. However, in the setting of pulmonary hypertension, they should suggest PVOD and PCH. They are probably secondary to venous congestion, veno-lymphatic shunts and angiogenetic factors associated with these diseases.