Yes, a lung mass if large enough (greater than about 1-2mm) has a good chance of showing up on an MRI. From what I have read the MRI is about 80% effective on picking up lung masses. After I had so many CT Scans that radiation became a concern they now have me take yearly MRI scans instead. If they did find something with the MRI they would probably want to follow up with a CT Scan anyways to verify however...

Dave