Plain English summary Patients should be involved in the design, conduct and dissemination of research that affects them. Patient involvement leads to empowerment and enhances the quality of research. Differing motives and expectations between researchers and patients involved can hamper involvement. We wanted to learn more about patients’ and researchers’ motives and expectations in order to improve the benefits of involvement for all parties. We implemented a patient board with ten patients and five researchers for a trial on urinary tract infections (UTIs). We asked each patient and researcher about his or her motivation and expectations regarding the patient board. We found that patients’ motivations included the wish to improve the treatment of UTIs, to support patient involvement as a principle, and to enhance the benefit of others. Furthermore they were interested in learning how a patients’ board works and in exchanging with peers and scientists. In addition, a (modest) monetary incentive for involvement was welcomed.Researchers were motivated by the possibility to improve research and to contribute to the empowerment of patients. They also wanted to enhance their career opportunities, to learn more about patient involvement and to meet the increasing demand for it. Some patients expressed insecurity about their roles and tasks in the patient board. Among the researchers, some envisaged a rather passive role for themselves in the patient board while others expected to take over a more active role. Researchers emphasized that the ways and the means of communication between the researchers and the patients should be explicitly discussed. Abstract Background It has been increasingly recognized that patients should be actively involved in the design, conduct and dissemination of research. Besides empowering patients and democratizing research, involvement can enhance the quality of research and the development of equitable healthcare solutions. Differing motives and expectations between researchers and involved patients can hamper the conduct of involvement. However, little is known about patients’ and researchers’ motivations for involvement. Our aim was to study the motivation and expectations of patients and researchers towards patient and public involvement (PPI). Methods We implemented a patient board comprising ten patients and five researchers for a randomized controlled trial on the treatment of urinary tract infections (UTI). Prior to the first board meeting, we conducted telephone interviews with all researchers and patients regarding their motivation for involvement in the patient board and their expectations. The interviews were analyzed using thematic qualitative text analysis. Results Patients’ motivations included interest in improving UTI treatment, in supporting PPI, engaging for the benefit of others, exchanging with peers and scientists as well as in the methods of the board and the monetary incentive. Researchers wanted to improve research, enhance their professional development, empower patients, meet the formal demand for PPI, and learn about PPI. Regarding expectations, patients expressed insecurities about their roles, tasks and topics of discussion. They wished for an open exchange and hoped their involvement would make an impact. Researchers’ expectations for their own roles ranged between being a rather passive supporting force and active engagement in the board. The question of how to ensure the communication between the trial team and the patient board was of high importance for the researchers. Conclusions Patients’ and researchers’ motives and expectations were similar in some aspects but differed regarding agenda setting and understanding of their roles. Getting to know patients’ and researchers’ motivations and expectations at the beginning allowed us to anticipate potential conflicts or disappointments early on and to take them into consideration during the conduct of our PPI.