ABSTRACT Objective: To explore diagnostic preferences among individuals with confirmed or suspected endometriosis to inform the development of patient-centered diagnostic strategies. Design: Qualitative study using semi-structured focus group discussions and grounded theory methodology. Setting: Tertiary gynecology clinic and a specialized diagnostic imaging center; focus groups conducted via videoconference. Population: Twenty-five individuals aged 21 to 56 years with confirmed or suspected endometriosis, recruited from two clinical sites between November 17, 2023, and August 15, 2024. Methods: Semi-structured focus groups were conducted, transcribed verbatim, anonymized, and analyzed using grounded theory. Open, axial, and selective coding were performed iteratively by two independent researchers. Discrepancies in coding were resolved through discussion or adjudication by a third analyst. Thematic saturation guided the conclusion of data collection. Main outcome measures: Patient-identified themes regarding diagnostic preferences, barriers, and facilitators in endometriosis care. Results: Eight major themes emerged: (1) diagnostic challenges and delays, (2) patient advocacy and self-advocacy, (3) importance of provider expertise and trust, (4) desire for visual confirmation and tangible validation, (5) emotional and psychological impact of the diagnostic journey, (6) diagnostic preferences and risk tolerance, (7) practical and institutional needs for formal diagnosis, and (8) educational needs and knowledge gaps among healthcare professionals and health service users. Conclusion: This study presents a patient-informed framework to guide diagnostic decision-making in endometriosis care. By centering patient perspectives, it supports the development of diagnostic strategies that are clinically sound, psychologically validating, and responsive to broader social and institutional needs. These findings provide foundational insights for the prospective development of a discrete choice experiment in a subsequent phase of the IPEDT study. Funding: This research did not receive any specific funding from public, commercial, or not-for-profit agencies. Key words: endometriosis, diagnostic preferences, grounded theory, patient-centered care, qualitative research, imaging, visual confirmation