Background/Aims: The adenoma detection rate (ADR) of screening colonoscopies performed by trainees is often lower than that of colonoscopies performed by experts. The efficacy of cap-assisted colonoscopy (CAC) in adenoma detection is well documented, especially that of CACs performed by trainees. Endocuff, a new endoscopic cap, is reportedly useful for adenoma detection; however, no trials have compared the efficacy of Endocuff-assisted colonoscopy (EAC) and CAC conducted by trainees. Therefore, the present study retrospectively compared the efficacy between EAC and CAC in trainees. Methods: This was a single-center, retrospective study involving 305 patients who underwent either EAC or CAC performed by three trainees between January and December 2018. We evaluated the ADR, mean number of adenomas detected per patient (MAP), cecal intubation rate, cecal intubation time, and occurrence of complications between the EAC and CAC groups. Results: The ADR was significantly higher in the EAC group than in the CAC group (54.3% vs. 37.3%, p=0.019), as was the MAP (1.36 vs. 0.74, p=0.003). No significant differences were found between the groups with respect to the cecal intubation rate or cecal intubation time. No major complications occurred in either group. Conclusions: Our results suggest that EAC exhibits increased ADR and MAP compared to CAC when performed by trainees. Clin