Approximately one third of patient appointments in health care result in failures, leading to patient risk and sizable resource "waste". Existing interventions to alleviate the no-shows often target the patients. The underlying reason behind these interventions is a view that attendance/non-attendance is solely the patient's problem. However, these interventions often prove ineffective and can perpetuate social biases and health inequalities, leaving behind the more vulnerable or disadvantaged patients (in terms of social, economical, linguistic factors, etc.). A more holistic understanding of no-shows is needed to optimize processes, to reduce waste and support vulnerable patients. This study aims to gain a deeper and more comprehensive understanding of the causes, mechanisms and recurring patterns and elements contributing to non-attendance at Danish hospitals in the Region of Southern Denmark. It emphasizes the patient perspective and analyses the relational and organizational processes surrounding no-shows in healthcare. Additionally, the study aims to identify effective communicative strategies and organizational processes that can support development and implementation of successful interventions. The research employs mixed quantitative-qualitative methods, encompassing four analytical projects focusing on non-attendance patterns, patient knowledge and behaviour, management of hospital appointments, and in-situ communication. To address the complexity of no-shows in healthcare the study incorporates various data sources. The quantitative data sources include the electronic patient records, the Danish central registries, the Danish National Patient Registry, and the Register of Medicinal Product Statistics. Baseline characteristics of patients at different levels are compared using Chi2 and Kruskal-Wallis tests. The qualitative studies involve observational data, individual semi-structured interviews with patients and practitioners, and video recordings of patient consultations. This paper presents the protocol of the study, which was funded by the Novo Nordisk Foundation in July 2022. The study was registered with The Danish Data Protection Agency (Registry ID: 22/54791) and with The Open Patient Data Explorative Network (Registry ID: OP_1800) in January 2023. Recruitment started in February 2023. It is anticipated that the quantitative data analysis will be completed by the end of September 2023, with the qualitative investigation starting in October 2023. The first study findings are anticipated to be available by the end of 2024. The existing research on non-attendance in Danish healthcare is inadequate in addressing relational and organisational factors leading to hospital no-shows. Interventions have had limited effect, high-lighting the Danish healthcare system's failure to accommodate for vulnerable patients. Effective interventions require a qualitative approach and robust ethnographic data to supplement the description and categorization of no-shows at hospitals. Obtaining comprehensive knowledge about the causes of missed patient appointments will yield practical benefits, enhancing safety, coherence and quality of treatment in healthcare.