Purpose: Obesity is known to be associated with colorectal adenoma (CRA) and colorectal cancer (CRC); yet colonoscopy is not considered an essential preoperative evaluation before bariatric/metabolic surgery. The aim of this study was to clarify the clinical significance of preoperative colonoscopy for obese Japanese patients. Methods: The subjects of this retrospective study were 114 patients who underwent screening colonoscopy before bariatric/metabolic surgery. Multivariate analyses were performed to evaluate the independent predictors of CRA/CRC among the characteristics identified as significant or nearly significant by univariate analyses. Results: Colonoscopy revealed abnormal findings indicating the need for biopsy or polypectomy in 20 of the 114 patients (17.5%), and CRA was diagnosed in 13 patients (11.4%). Three patients (2.6%), who were all ≥ 56 years old, had a CRA ≥ 10 mm in diameter. The multivariate analysis showed that older age and male sex were significant predictors of CRA/CRC, which was identified in 46.2% of the male patients aged ≥ 46 years. Conclusion: Our findings suggest that older age and male sex may be risk factors for CRA/CRC in obese Japanese candidates for bariatric/metabolic surgery; thus, preoperative colonoscopy should be considered for these high-risk patients. [ABSTRACT FROM AUTHOR]