An ultrasonic diagnostic imaging system is described in which two planes of a volumetric region which are in different elevation planes are scanned in real time. In one embodiment the two planes are scanned with less than the maximum number of scanlines which the transducer can transmit in a single plane. A user control enables the two planes to be moved laterally without moving the transducer probe. In another embodiment each image plane contains a color box depicting flow or motion in the same respective position in the image. The color boxes of the two images can be sized and positioned in tandem so that both are in the same corresponding area of the two images.