Eight researchers from Ghana and Benin, with different backgrounds but all co-operating within the Convergence of Sciences project, conducted diagnostic studies as a first step of their research aimed at developing technologies together with resource-poor farmers. The purpose of including diagnostic studies was to increase the likelihood that the resulting technologies would be grounded in the needs and opportunities of these farmers. To better understand the potential of diagnostic studies for improving the contribution of agricultural research to farmers’ livelihoods, a comparative study was conducted of the diagnostic studies carried out by the eight researchers. This research on agricultural research was participatory in that its results were arrived at in consultation with the eight researchers. The comparison revealed that diagnostic studies identified and established forums of stakeholders, especially of farmers, who were to play key roles in the co-construction of knowledge during the field experimental phase that followed the diagnostic studies. The diagnostic studies gave farmers a say in the design and conduct of the experimental phase which allowed them to influence the research process in the direction of developing and testing technologies that work in their circumstances and that satisfy their needs and priorities. In addition, the diagnostic studies have led to transparent choices with respect to the selection of sites, farmers and experiments. Furthermore, the conditions for negotiation were created. Finally, the diagnostic studies played a crucial role in making the partners within the Convergence of Sciences project aware of the importance of contextual framework conditions in determining the relevance of the project.