This is a prospective comparative clinical study including 30 patients previously diagnosed to have moderate to severe pulmonary valvular stenosis to compare between the pulmonary valve annulus by 2D echo , RT-3D echo versus Angiographic catheter calibration in the catheter laboratory before transvalvular balloon angioplasty dilatation. This detected the superiority of the RT-3D images in visualization of the thickened valvular cusps, its motility, fissuring of the commissures and calculation of the valve annulus and surface area regarding the choice of the appropriate size of the balloon for dilatation.