Image transmission with JPEG2000 can be speeded up by using regions of interest (RoIs). By such a mechanism, parts of an image not belonging to RoIs can be transmitted later or encoded at a lower bit rate. This paper describes a flexible dynamic RoI-scheme which supports the definition and handling of arbitrarily-shaped RoIs in JPEG2000. The scheme supports the dynamic definition and prioritization of new and existing RoIs at any time during image transmission. This can be done without having to decode and re-encode the JPEG2000 datastream. To reach this, we use the flexible Precinct/Layer-mechanism of the standard. The proposed scheme is fully compliant with the JPEG2000Baseline-Codec.