The risk of flooding in urban areas could be better approached by complementing conventional sewer systems with sustainable urban drainage systems (SUDS) for storm-water management. This may be the case for developing world cities like Dar es Salaam with incomplete sewer services, as well as cities like Copenhagen with fully developed sewer systems. This paper explores some theories relevant to understanding how the implementation of SUDS may be one option for supporting a transition towards sustainable urban water management (SUWM). Using interviews, document analysis and observation, a comparison of the opportunities and barriers to the implementation of SUDS in Dar es Salaam and Copenhagen is presented. The results indicate that a bottom-up approach in Dar es Salaam is important, with the community level taking the lead, while in Copenhagen the top-down approach currently employed is promising. The ability of the institutional frameworks of both cities to support the implementation of SUDS is also discussed.