Background and aims The purpose of this study was to determine the accuracy, interobserver variability, timing and discordance with relaparotomy of postoperative radiological examination of colorectal anastomoses. Patient/methods From 2000 to 2005, 429 patients underwent an ileocolonic, colo-colonic, or colorectal anastomosis. Radiological examination of the anastomosis was not performed routinely, but only when there were clinically signs of leakage. Radiological imaging was reviewed by an independent radiologist and medical records were retrospectively analyzed. Clinical anastomotic leakage was the standard of reference and defined as leakage confirmed during relaparotomy, drainage of pus per anum or as an anastomotic defect identified at digital examination. Results Radiological evaluation of the anastomosis was performed in 91 patients (21%): CT in 27 patients, contrast radiography in 40, and both imaging modalities in 24 patients. The interobserver variability of CT and contrast radiography was 10% and 14%, respectively. The sensitivity and negative predictive value of imaging of the anastomosis was 65% and 73%, respectively. Anastomotic leakage was found in 11 of 21 patients (52%) who underwent relaparotomy despite negative imaging. Three of 36 patients (8%) with a diagnosis of anastomotic leakage based on radiological examination had an intact anastomosis at relaparotomy. Conclusion Radiological imaging of the anastomosis after colorectal surgery should be restrictively applied and interpreted with caution because of the high false-negative rate and the substantial interobserver variability.