Sick teen missing from Brisbane hospital

An urgent appeal has been launched to find a sick 16-year-old boy missing from Brisbane's Lady Cilento Children's Hospital.

William Latter was last seen leaving the Woolloongabba health facility about 6pm on Wednesday.

He was spotted a short time later at South Bank, heading towards the CBD, but has not been seen since.

Inspector Jo-Anne Henderson said police were "deeply concerned" about William's safety and wellbeing because he was suffering from a medical condition.

"This young boy is of a very trusting nature," she said on Thursday.

"He is aware of his medical condition and may seek assistance if he starts to feel unwell."

Insp Henderson said William and his mum, who are originally from NSW, had been living in Brisbane while he received ongoing medical treatment.

He was not a hospital inpatient at the time of his disappearance.

Insp Henderson said police were not aware of any factors that contributed to William's decision to leave and said he could have just been "taking a timeout".

He is described as Caucasian, 155cm tall, with a slim build, brown eyes and brown hair.

He was last seen wearing a black baseball cap, pink or salmon shirt and tan-coloured pants.

Insp Henderson said William also had his "prized" rainbow-coloured micro scooter with him, but no mobile phone or cash.

Anyone with information about his whereabouts is urged to contact police.