This paper gives an introduction to technologies and methodologies to measure performance of MPEG-21 applications in mobile environments. Since resources, such as processing time, available memory, storage, network, and battery time, are very sparse on mobile devices, it is important to optimize technologies to use as little as possible of those resources. To identify possible optimization points for MPEG-21 technologies, performance measurements technologies are applied on a prototype implementation of MPEG-21 Digital Item Declaration and Digital Item Processing. The upcoming MPEG-21 its goal is providing transparent and augmented use of multimedia resources across a plethora of networks and devices. The prototype, which has been implemented on the J2ME platform, gives information about possible bottlenecks when designing MPEG-21 based applications. The results of the measurements are discussed and used to identify which improvements need to be realized to reduce memory and processor consumption when implementing the discussed parts of the MPEG-21 standards on a mobile platform. This paper ends with a discussion and concluding remarks.