GPs will be inviting around 7,000 smokers and ex-smokers to take part in the Leeds Lung Health Check project.
It will involve a special type of x-ray called a screening CT scan that can detect very early signs of lung cancer.
The Yorkshire Cancer Research-funded scans will be carried out in a mobile unit based in supermarket car parks and shopping centres.
The project has been developed in partnership with Leeds Teaching Hospitals NHS Trust, the University of Leeds and Leeds City Council.
Dr Kathryn Scott, chief executive at Yorkshire Cancer Research, said: “As well as saving lives, this trial will provide vital evidence that may help the government decide how to introduce a national lung cancer screening programme in the UK.”
Margaret Marshall, 82, from Whitkirk, was diagnosed with lung cancer aged 75 by chance after undergoing a full body scan for another condition.
A cancerous nodule was removed during keyhole surgery
She said: “I had no symptoms at all, even after the nodule had grown I didn’t know was wrong. That’s why screening for lung cancer is so important. It’s vital it’s found early.”
Mrs Marshall added: “I feel like the luckiest person on earth.”
Grandfather Roy Smith, 74, from Rothwell, was diagnosed with lung cancer in 2007.
He had coughed up blood one morning as he left the house to go to work and immediately decided to make an appointment to see his GP.
Mr Smith had a CT scan which revealed he had lung cancer and he underwent an operation to have his right lung removed followed by chemotherapy and radiotherapy,
Tests showed his cancer was mainly caused by exposure to asbestos when he worked at power stations.
However, he had also smoked throughout his life.
Mr Smith said: “Finding cancer early is crucial.
“If I hadn’t decided to see my doctor, I might not be here today.”
He added: “If you’re given the opportunity to have a check, you should take it. It could save your life.”
The mobile screening unit will be at the White Rose shopping centre in Leeds from today (Tues Nov 6) to Saturday November 17.
It will then move to Elland Road from Monday December 10 to Friday December 21.
Dr Mat Callister, consultant in respiratory medicine at Leeds Teaching Hospitals NHS Trust, estimates more than 300 lung cancers will be detected during the four-year programme.
Dr Callister said: “We’re trying to find people who would otherwise arrive in our clinics in two or three years’ time with advanced cancer, and instead pick up their cancer at an early stage when we can cure their disease and save their lives.”