Missing Qld man 'simply walked out door'

A missing Cairns father of two comforted his waking children then simply walked out the front door the day he disappeared, police say.

Anthony Selir was last seen at his home in Mt Sheridan about 4am on Friday.

Authorities scoured bushland in the area on Wednesday to try to find him, but so far there's been no sign of the 29-year-old.

"He was last seen in the house with his wife and two young children," Detective Sergeant Brad McLeish said.

"He was comforting the children because they'd woken up.

"Then he simply walks out the front door and hasn't been seen since."

Selir's family are concerned for his welfare given recent erratic behaviour, possibly linked to drug use, he said.

He said Selir's mental health might have also deteriorated given his father has also been ill.

There is no evidence to consider it suspicious but there are concerns for his welfare given possible drug use.

* Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14 or MensLine Australia 1300 78 99 78.