OBJECTIVE Several studies have already shown the correlation between the right ventricle (RV) hemodynamic values and either glucose uptake or fatty acid uptake in the RV, respectively. However, there are few studies to compare the RV metabolic alteration before and after treatment for pulmonary hypertension. The aims of this study are to assess right ventricular glucose and fatty acid in chronic thromboembolic pulmonary hypertension (CTEPH) patients before and after pulmonary thromboendarterectomy and to examine whether there is a correlation between right ventricular glucose and fatty acid uptake. METHODS To assess glucose and fatty acid accumulation in the RV, [(18)F] fluoro-2-deoxyglucose (FDG)-positron emission tomography (PET) and (123)I-β-methyl iodophenyl pentadecanoic acid (BMIPP) imaging were performed in CTEPH patients before (FDG: n=20, BMIPP: n=13) and after (FDG: n=12, BMIPP: n=8) thromboendarterectomy. RESULTS Both [(18)F] FDG uptake and (123)I-BMIPP uptake in RV of post-PEA patients obviously decreased after this operation procedure (p<0.01). The right ventricle [(18)F] FDG uptake was also significantly correlated with (123)I-BMIPP uptake (r=0.45, p=0.04). CONCLUSIONS In this study, we observed that both glucose and fatty acid accumulated in the RV of patients with CTEPH. Although the exact details of the altered energy metabolism in the stressed RV remain unknown, this is the first study to evaluate both glucose and fatty acid uptake before and after thromboendarterectomy in patients with CTEPH, even though the number of the patient is limited.