Background and Aims: Mucosal healing [MH] is an important goal for patients with Crohn's disease [CD], yet is incompletely characterised. We investigated whether MH differed by segments across the colon and ileum in patients who received adalimumab maintenance treatment in the EXTEND study. Methods: In this double-blind study in adults with moderate to severe ileocolonic CD and mucosal ulceration, all patients received adalimumab induction [Week 0, 160 mg; Week 2, 80 mg]. At Week 4, patients were randomised to 40 mg adalimumab or placebo every other week until Week 52. In this post-hoc analysis, MH was assessed by CD Endoscopic Index of Severity [CDEIS], Simple Endoscopic Score for CD [SES-CD], and Colonic and Ileal Global Histologic Disease Activity Scores [CGHAS/IGHAS]. Results: Baseline endoscopic severity was similar across segments. At Week 52, mean changes in CDEIS surface involved and ulcerated surface were -68.5% to -90.6% in the rectum, sigmoid/left colon, and transverse colon compared with -22.3% to -50.0% in the right colon and ileum. Favourable shifts by Week 52 in ulcer size and ulcerated surfaces per SES-CD were more pronounced in the rectum, sigmoid/left colon, and transverse colon vs the right colon and ileum. At Week 52, CGHAS and IGHAS healing was more common in the colon [28.3%] vs the ileum [21.2%]. Conclusions: This analysis suggests differing propensities of the ileocolonic segments to heal endoscopically during adalimumab treatment. In the sigmoid/left and transverse colon, higher MH rates may be achieved, compared with the ileum, in patients with moderate to severe CD.