The man still missing off the north Queensland coast after his boat was found drifting on Tuesday is a hospital doctor, Queensland Health has confirmed.

Dr Richard Thomas, 55, who works at Atherton Hospital, about 50 kilometres south-west of Cairns, was identified as the missing man by the Cairns and Hinterland Hospital and Health Service.

Police want to speak to anyone who saw Dr Thomas' 5.6-metre vessel. Credit:Queensland Police Service

The health service did not release a photo of Dr Thomas or any further information "out of respect for his family’s privacy", but said in a statement affected staff were being supported.

The search continued for Dr Thomas on Friday, with police vessels and a rescue helicopter involved in scouring the waters off Innisfail, south of Cairns.