Patients who fail to maintain adequate respiration may need long-term mechanical ventilation (LTMV) in shorter or longer periods. Patients using LTMV constitute a heterogeneous group with respect to age, diagnoses and disease progression. Norwegian data suggests considerable regional differences in the use of LTMV. The Norwegian Directorate of Health recently prepared new guidelines for the use of LTMV outside hospitals. The Norwegian Knowledge Centre for Health Services was commissioned to prepare a systematic review on the efficacy of LTMV. This is the first of three reviews, and here we summarize evidence on the effectiveness of LTMV for patients with neuromuscular disorders and for patients with central respiratory failure. LTMV may be associated with some degree of life extension and improved quality of life for patients with amyotrophic lateral sclerosis, at least for patients with good bulbar function. The quality of evidence is low, and it is not possible to draw firm conclusions about the real effect. LTMV can be associated with life extension among hypoventilated patients with Duchenne muscular dystrophy, but the quality of evidence is low, and it is not possible to draw firm conclusions about the real effect. Across patients with various neuromuscular diagnoses, it seems that LTMV may be associated with fewer hospital admissions, and that invasive LTMV is associated with greater risk of complications and hospitalization than non-invasive LTMV. The quality of evidence is low, and we can not draw firm conclusions about the real effect. For some diagnoses, for example central respiratory failure, we were not able to identify any research fulfilling our inclusion criteria.