There is an increasing need to demonstrate the return on medical research investment through benefit to patients, society and the economy. Patient-reported outcomes (PROs), such as quality of life and symptom data, are increasingly collected in clinical trials and may provide evidence, which can lead to a range of impacts. However it is unclear whether PRO impact is realised in practice. In addition, the different types of impact associated with PRO trial results, their barriers and facilitators, and appropriate impact metrics are not well defined. The doctoral research constituting this thesis adopted a mixed-methods approach with the aim of: a) synthesising existing methodological frameworks for healthcare research impact; b) determining the range of potential impacts associated with PRO data collected in trials, identifying potential PRO impact metrics and barriers and defining common facilitators to maximise PRO impact and; c) examining real-world evidence of PRO trial data impact and highlight optimal pathways to such impact. A number of studies were undertaken to address the aims. First, a systematic review of the literature identified 24 existing non-PRO-specific frameworks and over 80 impact metrics, which were then synthesised into a novel impact matrix and a simplified consolidated methodological framework for use by researchers and other stakeholders to help maximise the impact of healthcare research. Second, informed by this framework, an additional systematic review sought to determine the potential impact of PRO data collected in clinical trials and examined real world evidence of PRO trial data impact based on Research Excellence Framework (REF). This systemic review suggested that PRO trial data has the potential to inform clinical practice, clinical guidelines and, health policy; support drug approval, pricing and reimbursement decisions and; inform clinical and shared decision-making and consent for treatment. Furthermore, this second systematic review highlighted perceived methodological problems regarding the design, conduct and analysis and reporting of PRO data from clinical trials; which may hinder the impact of PRO data from clinical findings. Potential facilitators aimed at maximising PRO trial impact were also identified. The review identified 12 (n=69, 17%) REF 2014 impact case studies, which reported impact directly attributable to PRO findings. Including changes to international clinical guidelines and national guidelines, influencing cost-effectiveness analysis and drug approvals. Finally, in order to gain deeper understanding about the topics identified in the second systematic review, 24 semi-structured qualitative interviews were conducted with international stakeholders. Interviewees suggested PRO trial findings could lead to impact in the five impact categories identified in the aforementioned 'pathways to research impact' methodological framework. However, it was suggested that broader international stakeholder collaboration is required to tackle existing barriers and maximise the realisation of PRO trial impact on patients and society. In conclusion, this thesis has identified a range of potential impacts from PRO data which may benefit patients and society. However, a number of barriers need to be addressed to fully realise these benefits. This research highlights that the measurement of research impact, and specifically PRO research impact, is an essential exercise to better allocate limited funding, provide accountability and minimise research waste. Nonetheless, determining and implementing impact metrics is a complex task and will require greater stakeholder collaboration and engagement throughout the research pathway.