Résumé: Background: Previous studies in the literature have shown significant variations in colonoscopy performance, even when medical factors are taken into account. This study aimed to examine the role of non-medical factors (i.e. embodied in health care system design) as possible contributors to variations in colonoscopy performance. Methods: We used patient data from a multicenter observational study conducted between 2000 and 2002 in 21 centers across 11 western countries. Variability was captured through two performance outcomes (diagnostic yield and colonoscopy withdrawal time), jointly studied as dependent variables using a multilevel two-equation system. Results: Results showed that open-access systems and high-volume colonoscopy centers were independently associated with a higher likelihood of detecting significant lesions and higher withdrawal durations. Fee for service (FFS) payment was associated with shorter withdrawal durations, and had an indirect negative impact on the diagnostic yield. Teaching centers exhibited lower detection rates and higher withdrawal times. Conclusions: Our results suggest that gate-keeping colonoscopy is likely to miss patients with significant lesions and that developing specialized colonoscopy units is important to improve performance. Results also suggest that FFS may result in a lower quality of care in colonoscopy practice and highlight that longer withdrawal times do not necessarily mean higher quality in teaching-centers.