BACKGROUND: Revascularisation of a chronic total coronary occlusion (CTO) impacts the coronary physiology of the remote myocardial territory. AIMS: This study aimed to evaluate the intrinsic effect of CTO percutaneous coronary intervention (PCI) on changes in absolute perfusion in remote myocardium. METHODS: A total of 164 patients who underwent serial [15O]H2O positron emission tomography (PET) perfusion imaging at baseline and three months after successful single-vessel CTO PCI were included to evaluate changes in hyperaemic myocardial blood flow (hMBF) and coronary flow reserve (CFR) in the remote myocardium supplied by both non-target coronary arteries. RESULTS: Perfusion indices in CTO and remote myocardium showed a positive correlation before (resting MBF: r=0.84, hMBF: r=0.75, and CFR: r=0.77, p<0.01 for all) and after (resting MBF: r=0.87, hMBF: r=0.87, and CFR: r=0.81, p<0.01 for all) CTO PCI. Absolute increases in hMBF and CFR were observed in remote myocardium following CTO revascularisation (from 2.29±0.67 to 2.48±0.75 mL·min-1·g-1 and from 2.48±0.76 to 2.74±0.85, respectively, p<0.01 for both). Improvements in remote myocardial perfusion were largest in patients with a higher increase in hMBF (β 0.58, 95% CI: 0.48-0.67, p<0.01) and CFR (β 0.54, 95% CI: 0.44-0.64, p<0.01) in the CTO territory, independent of clinical, angiographic and procedural characteristics. CONCLUSIONS: CTO revascularisation resulted in an increase in remote myocardial perfusion. Furthermore, the quantitative improvement in hMBF and CFR in the CTO territory was independently associated with the absolute perfusion increase in remote myocardial regions. As such, CTO PCI may have a favourable physiologic impact beyond the intended treated myocardium.