Objective: To compare image quality and radiation dose of high-pitch dual-source spiral cardiothoracic computed tomography (CT) between non-electrocardiography (ECG)-synchronized and prospectively ECG-triggered data acquisitions in young children with congenital heart disease. Materials and Methods: Eighty-six children (<= 3 years) with congenital heart disease who underwent high-pitch dual-source spiral cardiothoracic CT were included in this retrospective study. They were divided into two groups (n = 43 for each; group 1 with non-ECG-synchronization and group 2 with prospective ECG triggering). Patient-related parameters, radiation dose, and image quality were compared between the two groups. Results: There were no significant differences in patient-related parameters including age, cross-sectional area, body density, and water-equivalent area between the two groups (p > 0.05). Regarding radiation dose parameters, only volume CT dose index values were significantly different between group 1 (1.13 +/- 0.09 mGy) and group 2 (1.07 +/- 0.12 mGy, p < 0.02). Among image quality parameters, significantly higher image noise (3.8 +/- 0.7 Hounsfield units [HU] vs. 3.3 +/- 0.6 HU, p < 0.001), significantly lower signal-to-noise ratio (105.0 +/- 28.9 vs. 134.1 +/- 44.4, p = 0.001) and contrast-to-noise ratio (84.5 +/- 27.2 vs. 110.1 +/- 43.2, p = 0.002), and significantly less diaphragm motion artifacts (3.8 +/- 0.5 vs. 3.7 +/- 0.4, p < 0.04) were found in group 1 compared with group 2. Image quality grades of cardiac structures, coronary arteries, ascending aorta, pulmonary trunk, lung markings, and chest wall showed no significant difference between groups (p > 0.05). Conclusion: In high-pitch dual-source spiral pediatric cardiothoracic CT, additional ECG triggering does not substantially reduce motion artifacts in young children with congenital heart disease.