State Emergency Service (SES) volunteers and a helicopter will today continue their search for a man and woman missing in north Queensland.

The 48-year-old man and 53-year-old-woman have not been seen since lunchtime yesterday when they were walking with a tour group on sanddunes along the McIvor River, north of Cooktown.

Police said the couple told the group they would stop walking about 1.30pm because the man had a sore knee.

The group lost track of them and raised the alarm about 6.30pm when the couple failed to return to camp.

The pair are believed to be in good health.

Meantime, mobile phones have saved two separate groups bushwalking in national parks south-west of Brisbane over the weekend.

Park rangers will today guide a group of eight campers back to safety after they became lost on Mount Barney, near Beaudesert.

The group, which comprises two families, were able to send a text message to a friend's mobile phone in Brisbane, alerting authorities to their predicament.

Police said the two men, one woman and five children, who had been on a two-day camping trip, spent another night on Mount Barney and would be guided back to safety today.

In the second incident, an Ipswich couple are safe and well after spending a day lost on Mount Flinders, south-west of Brisbane.

The 31-year-old man and his 30-year-old wife, who live in Redbank Plains, used their mobile phone to call police after they became dioriented on their way up to Flinders Peak.

Police said a helicopter crew spotted a small fire the couple had built about 10.40pm and relayed its co-ordinates to a land-based search crew.

The couple were located and walked back to safety about 12.20am.