PROLOG All patients complying with the inclusion criteria (age >50 years and suspicion of lung cancer, based on clinical symptoms and /or history with including being a current or former smoker and other risk factors laid down by the Pre-PROLOG 1 study) are referred to an ordinary chest x-ray at the Department of Radiology OUH. The same day or the next day a PET/CT scan is performed at the Department of Nuclear Medicine, OUH. All patients will have both a chest x-ray and a PET/CT-scan.