In the thesis we discuss the use of SOAP and REST web services on Android-based mobile devices. We learn, what web services are, how they work and why we need them. We present both leading approaches, look at how they work and what is being exchanged between the client and the server. We study, how each technology is supported on Android-based mobile devices and which libraries are available for use. With this knowledge we develop a mobile application that connects to a web service and transfers files of various sizes. This enables us to further compare both technologies from a technical point of view, where we are mainly interested in the final size of the mobile application, amount of data transferred, number of packets transferred, transfer time and throughput. The results and findings will ease the choice of the right technology for mobile application developers.