Background The most common cardiac tumors in young children are rhabdomyoma and fibroma, and prognosis depends on the tumor's characteristics. In the present study electron-beam computed tomography (EBT) was used to evaluate tumor characteristics and myocardial perfusion in 6 children with cardiac tumors. Methods and Results Five children had rhabdomyomas and 1 had a fibroma. In the precontrast study, the computed tomography numbers of rhabdomyomas were higher and those of the fibroma were slightly lower than those of the normal myocardium. In the early postcontrast study, the size, location, shape and number of the tumor were clearly detected, and in the late postcontrast study, the fibrous characteristics of the tumor were seen. The fibroma contained calcification and 2 rhabdomyomas contained a fat density spot. In the cine-mode study, both the tumor and ventricular wall motion could be simultaneously evaluated. There was a filling defect of the left ventricular myocardium on the early postcontrast scan of 1 child with a rhabdomyoma and dyskinetic wall motion at the same region in the cine-mode study. Conclusion EBT was useful for evaluating tumor characteristics in children. (Circ J 2005; 69: 1352 - 1356)