: Long-term non-invasive ventilation (LTNIV) for the stable hypercapnic chronic obstructive pulmonary disease (COPD)-patients have been a subject of much debate in the last two decades. The aim of this study was to compile the current knowledge on LTNIV in order to evaluate the effects on mortality and hypercapnia. : Literature search in Pubmed, Ovid, and Embase for RCTs in Humans from January 2000 through January 2019 in written English. : Six studies with a total of 861 patients were included. LTNIV in stable hypercapnic COPD patients significantly reduced PaCO but only one study found significant reduction in mortality. : Our meta-analyses demonstrate that LTNIV significantly reduced PaCO in stable patients with chronic hypercapnic respiratory failure compared to standard care alone, and subgroup analyses on studies with a predefined plan for ventilation, showed a considerable trend towards significant reduction in mortality. The take home messages on LTNIV in stable hypercapnic COPD are: It is essential that the patients have stable chronic hypercapnia.The degree of stability can best be assessed after a minimum of 2 weeks following an acute hypercapnic respiratory failure (AHRF).It is important to ventilate the patient with the goal to reduce PaCO by at least 20% or below 6.5 kPa.