Selenoprotein-related myopathy (SEPN1-RM) is a rare disease with a variable clinical presentation. The selenoprotein N1 gene (SEPN1) mutation causing this congenital muscular dystrophy was identified in 2001. Sleep-disordered breathing (SDB) may occur in young SEPN1-RM patients who are still able to walk. We report here the cases of two children with SEPN1-RM who presented with SDB at the ages of 7 and 12 years and for whom long-term nocturnal noninvasive ventilation yielded significant improvement. Based upon literature review and our current cases, it seems that there is no obvious relationship between time since SDB onset and outcome of pulmonary function tests or limb muscle weakness. We therefore suggest that sleep-disordered breathing should systematically be screened for in patients with SEPN1-RM, at regular intervals using nocturnal polysomnography.