We describe the occurrence of vasovagal reaction in two patients who underwent CT colonography (CTC). The patients, asymptomatic, were submitted to CTC in one case after right colectomy and in one case for screening purposes. The vasovagal symptoms occurred after pneumocolon and acquisition in the prone decubitus, and included headache, hypotension, bradycardia, cold sweat and pallor, nausea, and diaphoresis. Abdominal pain was also referred. All symptoms resolved within 30 min to 3 h from their onset. In all cases the vasovagal reaction occurred after prone decubitus. CTC images showed a significant distension of the small bowel. Vasovagal reactions are potential complications of CTC.