Dr Lillemoe has served as Secretary, President and Chairman of the Board of Trustees of the Society for Surgery of the Alimentary Tract. He has served as President of the Society of Clinical Surgery, Secretary and President of the Society of University Surgeons, and as the Recorder for the American Surgical Association. He is a Senior Director of the American Board of Surgery.

Dr. Lillemoe's clinical research interests are in pancreatic cancer, IPMNs and other benign pancreatic disorders, and biliary tract injuries. His bibliography lists over 300 journal articles and 115 book chapters. He has served as a visiting professor over 70 times and has spoken nationally and internationally on over 315 occasions. He is currently the Editor of one of the leading surgical texts Surgery: Scientific Principles and Practice and is Editor-in-Chief of Annals of Surgery.