There has been an increase in the size and range of North-South health research partnerships since the 1990s. Current literature tends to stress the need for partnership and associated principles, but recognises the difficult context of structural inequality and historical legacies. Critics point to continuing neo-colonialist attitudes to research, which are unhelpful for the development of mutually beneficial collaborations. Such dynamics have parallels with the European folktale of Cinderella and the Ugly Sisters, the latter using their advantage of wealth and position to exploit their step-sister. Little literature is available on how to address this situation for the principles of partnership to be integrated into project design, implementation and dissemination. This article examines processes and dynamics within North-South collaborations in health research through two different case studies presented from Northern perspectives. Each case study focuses on distinct aspects of research collaborations. The first, a North-South partnership project in Bangladesh, highlights issues of capacity building, use of data and publications. The second case, a Doctoral study in Thailand, examines the reliance on contributions by Southern partners, responsibility to the local setting and the practice of reciprocity. The article then turns to Southern researchers' reflections, explored in semi-structured interviews, on themes identified by Northern researchers as important concerns in research collaborations. The authors conclude that advantage should be taken of the fact that Southern and Northern colleagues often share similar values regarding research collaborations, but difficulties exist in implementation partly due to historically rooted and current inequalities. Practical arrangements are suggested which may help to address the commonly assumed roles of the North as 'provider' of funding and ideas, and of the South as 'receiver' in an environment with little scope for action.