In 5-10% of patients it is not possible to achieve a complete endoscopic examination of the colon, because of obstructing cancer, excessive length of the colon, anatomical abnormalities or adhesions. Virtual colonoscopy is currently capable of investigating the colic lumen with a non-invasive technique, with high specificity and sensitivity. From January 2005 to July 2007 we treated 21 patients with obstructing neoplastic colorectal lesions, preventing a complete endoscopic examination. In all patients we performed a virtual colonoscopy, which revealed the presence of synchronous lesions (19%): a pedunculated polyp in two cases, a sessile polyp in one case and a right colonic vegetating lesion. In the 21 patients studied we performed a follow-up colonoscopy 3 months after the surgical treatment. No other endoluminal lesions were found, confirming the results of virtual colonoscopy. In our experience virtual colonoscopy presented 100% sensitivity and specificity. In this selected group of patients with obstructing lesions of the colon, virtual colonoscopy enables the surgeon to evaluate the entire colon, avoiding the execution of an intraoperative colonoscopy and possible surgical reintervention due to the finding of synchronous neoplastic lesions at postoperative follow-up endoscopy.