A mouthpiece for oral delivery for oral delivery of CPAP treatment has a vestibular shield for location between the teeth and lips/cheeks of a wearer. The vestibular shield is formed from a very supple material and is dimensioned to extend laterally into the buccal vestibule and vertically to overlap the gums. A gases pathway is provided through the vestibular shield and may include a hard plastic insert through the shield. A connection for connecting the mouthpiece to a breathing circuit is provided which reduces the transfer of forces caused by movement therebetween.