The advances of mobile technologies like portable handheld-computers and wireless data transmission enabled the realization of mobile workflow management systems. In such systems workflow activities can be performed using mobile devices like PDAs or smartphones. Further, the availability of locating technologies like the Global Positioning System (GPS) allows determining the spatial position of a mobile computer and stimulated the emergence of a new class of mobile application, the so called “Location-based Services”. The novel approach presented in this paper is to define location constraints for individual workflow activities when modeling a workflow schema to restrict the location where an activity can be performed. Restricting the location of activities to particular locations can help to mitigate mobility-specific usability and security issues. We introduce several types of such location constraints and suggest ways how to define them. A special focus is on “location rules” to automatically derive dynamic location constraints based on the mobile actor's current position.