Background and study aims: Large (≥ 20 mm) non-pedunculated colorectal lesions have high rates of synchronous neoplasia and advanced neoplasia. Synchronous neoplasia prevalence in patients with large pedunculated lesions is uncertain. We describe synchronous neoplasia in patients with large pedunculated colorectal polyps, using a cohort of patients with large non-pedunculated lesions as controls. Patients and methods: Retrospective assessment of a prospectively recorded database listing synchronous findings in patients with ≥ 20 mm colorectal lesions referred to a tertiary center for endoscopic resection. Results: At least 1 synchronous precancerous lesion was identified in 66 of 78 (84.6%, 95% CI 74.9-91.1) patients with large pedunculated lesions and 726 of 814 (89.2%, 95% CI 87.1-91.3) patients with large non-pedunculated lesions. Patients with large pedunculated lesions had mean 4.8 synchronous conventional adenomas, and 56% had ≥ 1 synchronous high-risk lesion (advanced adenoma or advanced serrated lesion), 49% had ≥ 1 synchronous advanced conventional adenoma, and 19% had a synchronous neoplastic lesion ≥ 20 mm. Patients with large pedunculated index lesions had comparable rates of synchronous polyps, adenomas, and sessile serrated lesions, and had higher rates of synchronous adenomas with villous elements (26.9%, 95% CI 18.3-37.7 vs. 15.6%, 95% CI 13.3-18.3; p = 0.01) as well as synchronous pedunculated polyps compared to patients with non-pedunculated index lesions (33.3%, 95% CI 23.8-44.4 vs. 9.5%, 95% CI 7.6-11.7; p < 0.001). Conclusion: In patients with large (≥ 20 mm) pedunculated colorectal lesions, rates of synchronous neoplasia and advanced synchronous neoplasia are high and comparable to or higher than rates of synchronous neoplasia in patients with large (≥ 20 mm) nonpedunculated colorectal lesions.