Workflow management systems (WFMS) are an emerging technology for supporting the coordinated execution of business processes by a group of users. One goal of introducing a WFMS into an enterprise is to integrate all personnel working on a business process into the system. This article describes a new approach to the integration of mobile users into a WFMS. This is of special interest because key personnel such as sales representatives and executives are often travelling and can only be integrated into the WFMS through mobile computing technologies. After introducing an architecture for mobile WFMS, we focus on the handling of one specific feature of mobile systems: the high diversity of environments in which mobile users operate. For handling this feature we have to implement adaptable software systems. In our approach, we start by introducing a formal model of mobile systems. This model offers a basis for the use of optimisation techniques to realise an adaptive mobile WFMS.