Background: Results of screening colonoscopy from Western countries reported adenoma detection rates(ADRs) of 30-40% while those from Asia had ADR as low as 10%. There have been limited data regardingscreening colonoscopy in Thailand. The objectives of this study were therefore to determine polyp and adenomadetection rates in Thai people, to evaluate the incidence of colorectal cancer detected during screening colonoscopyand to determine the endoscopic findings of the polyps which might have some impact on endoscopists to performpolypectomy. Materials & Methods: This study was a retrospective electronic chart review of asymptomatic Thaiadults who underwent screening colonoscopy in our endoscopic center from June 2007 to October 2010. Results:A total of 1,594 cases were reviewed. The patients had an average age of 58.3±10.5 years (range 27-82) and 55.5%were female. Most of the cases (83.8%) were handled by staff who were endoscopists. A total of 488 patients(30.6%) were reported to have colonic polyps. Left-sided colon was the most common site (45.1%), followed byright-sided colon (36.5%) and the rectum (18%). Those polyps were removed in 97.5% of cases and 88.5 % ofthe polyps were sent for histopathology (data lost 11.5%). Two hundred and sixty three cases had adenomatouspolyps, accounting for 16.5 % ADR. Advanced adenomas were detected in 43 cases (2.6%). Hyperplastic polypswere mainly located distal to the splenic flexure of the colon whereas adenomas were found throughout the largeintestine. Ten cases (0.6%) were found to have colorectal cancer. Four advanced adenomas and two malignantpolyps were reported in lesions ≤ 5 mm. Conclusion: The polyp detection rate, adenoma detection rate, advancedadenoma detection rate and colorectal cancer detection rate in the screening colonoscopy of Thai adults were30.9%, 16.5%, 2.6% and 0.6% respectively. Malignant transformation was detected regardless of the size andlocation of the polyps. Therefore, new technology would play an important role indistinguishing polyps.