A 15-year-old girl had no REM sleep presumably due to a pontine cavernous hemangioma was reported. Her brain MRI revealed a cavernous hemangioma extending from the dorsal pontine to the medulla. She manifested truncal ataxia, facial nerve palsy, and ocular motor apraxia. She could not sleep in the supine position due to the sleep apnea accompanied with loud snoring. Overnight polysomnography (PSG) was performed for detection of obstructive sleep apnea syndrome (OSAS). In addition to severe OSAS and Cheyne-Stokes-like respiration at wake after sleep onset, her 1st PSG study revealed no periods with rapid eye movement, EEG characteristic of REM sleep, atonia and variation on respiratory and heart rate. Even after effective therapy for OSAS with non-invasive positive airway pressure ventilation (NPPV), her 2nd PSG also failed to show stage REM. These findings suggest that this pontine cavernous hemangioma disturbed her REM-on system. This is the first report of an individual with long-term loss of REM sleep and a valuable case for the understanding of anatomical structures of the REM-on system and the role of REM in memory consolidation.