In this paper, a quality scalable coding for a selected region is presented. If one region is semantically more important than others, it is necessary for an image compression scheme to be capable of handling the regional semantic difference, because the information loss in the region of interest is more serious. We propose a quality scalable coding along with its model by introducing a quality scale parameter. It is a more extended and generalized image compression philosophy than the conventional coding. For an implementation of the proposed quality scalable coding, an H.263-based scheme is presented. This scheme controls temporal and spatial quality efficiently and improves the reconstructed image quality of the region of interest. (C) 1999 Elsevier Science B.V. All rights reserved.