Isabelle Pepin, 17, has become the focus of a police search since she went missing from her home in Laval on Thursday.
Pepin left school at around 2 p.m. and was expected to arrive home at about 3:30 p.m. but she never showed up.
She is without her medication and her life could be in danger without it.
Pepin has brown hair and eyes and stands 5'2" (1.58 m) and weighs 115 lb (52 kg).
Anybody with knowledge of her whereabouts is asked to contact police by phoning 911.
