BACKGROUND: Extracolonic findings are frequently recognized alongside colonic pathology at computed tomographic colonography (CTC). This study assessed the clinical impact of extracolonic findings in a symptomatic population at high risk of colorectal cancer. METHODS: CTC was performed in a consecutive cohort of patients assessed in a fast-track colorectal cancer clinic as being at high risk of colorectal cancer. A review of CTC findings and case notes was undertaken. Patients with extracolonic findings were followed up for at least 12 months. RESULTS: Thirty-one (13.8 per cent) of 225 patients investigated by CTC had colorectal cancer. Extracolonic findings were identified in 81 (53.3 per cent) of 152 patients with normal or non-neoplastic bowel findings, compared with 27 (37 per cent) of 73 patients with colorectal neoplasia (P = 0.025). Twenty-four patients (10.7 per cent) with extracolonic findings underwent further investigation or treatment. The median duration of investigation was 19.5 weeks. Seventy-five clinical events were recorded, including 14 surgical procedures. CONCLUSION: A prospective cost-benefit analysis of diagnostic CTC should be performed before it is established as a first-line investigation for colonic symptoms.