OBJECTIVE The authors present the findings of contrast-enhanced electrocardiogram (ECG)-gated cardiac computed tomography (CT) in 18 patients with probably spontaneous closure of muscular ventricular septal defect (VSD). METHODS The study included 2,725 consecutive patients referred to our hospitals for multidetector computed tomography (MDCT) coronary angiography. The patients were between the ages of 5 and 78 [mean+/-standard deviation (SD) 59+/-13.86] years, and 1,816 (66.6%) were male. Evaluating the images for coronary artery pathologies revealed pouches or sacs in the central muscular location of the septa of some patients. RESULTS All patient records were retrospectively reviewed, and 18 patients were found to have pouches or sacs in the interventricular septum location likely to be spontaneous closure of muscular VSD (0.66% prevalence). MDCT findings of these 18 patients correlated with their echocardiographic findings. Of the patients with muscular VSD, 13 were male and five were female. These 18 patients were initially referred due to indications such as chest pain (n=11), risk-factor assessment (n=3), coronary artery anomaly (n=1), suspected aberrant right subclavian artery due to dysphagia (n=1) and coronary artery bypass graft (n=2). CONCLUSIONS Our study shows that the incidence of spontaneous closure of muscular VSD with central septum location is probably higher than expected. Thus, some patients initially diagnosed with ventricular diverticula with an apical and marginal septum location may actually have spontaneously closed muscular VSD. This finding may affect previously reported rates of both ventricular diverticula and spontaneous closure of muscular VSD.