This dissertation focuses on the mechanisms, monitoring and management of patient and public involvement in hospital quality improvement (QI) interventions. Findings from a literature review generated an initial programme theory (PT) on active patient involvement in healthcare QI interventions (Paper 1). Empirical studies were also undertaken in order to describe what was actually happening in the hospital QI teams and what patients and professionals experience influence their joint involvement (Paper 2), and to compare hospital leaders’ and managers’ experiences of managing QI interventions involving patients and the public (Paper 3). Finally, it was studied how patient-reported measures stimulate patient involvement in QI interventions in practice (Paper 4). The research had a qualitative design. The approach was descriptive and comparative, and the studies were carried out prospectively. Data were collected in two hospital organisations in Sweden and in one hospital organisation in the Netherlands. Data collection methods were a literature search (Paper 1), interviews and field observations (Paper 2 and 3) and data collection meetings (Paper 4). Altogether, 93 team meetings and meetings between the team leaders and management were attended and a total of 20 days of study visits with different forms of meetings were made. Twelve patients, 12 healthcare professionals and 17 and 8 hospital leaders and managers, respectively, participated in the interviews and data collection meetings. Realist synthesis was used to formulate the initial PT (Paper 1). Constructivist grounded theory was used to analyse and describe what was happening in the QI teams and how it was experienced by the team members (Paper 2). To compare hospital leaders’ and managers’ different, contextual meanings in Sweden and the Netherlands, the reflexive thematic analysis informed by critical realism was used (Paper 3). To order, manage and map data from 31 examples of local QI interventions associated to patient-reported measures, the framework method was used (Paper 4). The results formulate a generic PT on the mechanisms, monitoring and management perspectives of co-produced QI interventions in hospital services where patients and the public are involved. The PT provides a hypothesis on the various mechanisms at play and outcomes obtained at the different levels of hospital organisations in the process. It is argued that focus should be on experiences, interaction, relationships and dialogue, integration of context, and the matching of hospital resources to patient and public demands and needs. Subsequently, the outcome will be the resources and reasoning interplay resulting in actions and processes, experiences and knowledge, ‘product’ benefits, emotions, judgements and motivations. Monitoring constitutes an important feedback loop to enable such learnings. The PT aligns the perspectives of the clinical microsystem, improvement science and the service-dominant logic, and has a potential to explain how patient and public involvement in QI interventions might work.