As Europe advances both the European Open Science Cloud (EOSC) and the European Health Data Space (EHDS), understanding how these two major initiatives interact is critical for researchers, data holders, and policymakers. This work directly supports the strategic goal of unlocking the potential of health data for research and innovation while minimising fragmentation, redundancies, and barriers to cross-border collaboration. This deliverable presents a comprehensive gap analysis of the interplay between the EOSC ecosystem and the EHDS regulation, covering data hosting and discoverability, interoperability and quality, and data processing. It targets researchers, research infrastructure operators, policymakers, Health Data Access Bodies, and technical implementers active in either or both ecosystems. The document maps the EOSC and EHDS landscapes across governance, infrastructure, interoperability, and data processing. A foundational distinction underpins the entire analysis: EHDS is a binding, top-down regulatory framework exclusively governing electronic health data — establishing legal bases, Secure Processing Environments (SPEs), and Health Data Access Bodies (HDABs) — whereas EOSC is a voluntary, federated, community-driven initiative spanning all scientific disciplines. The two are complementary but legally and operationally independent. Despite this distinction, several concrete synergies emerge. EOSC nodes could provide SPE-compliant infrastructure; metadata standards such as HealthDCAT-AP could be aligned across both ecosystems to improve data discoverability; authentication frameworks (eIDAS, AARC/Life Science Login) are already technically compatible; and EOSC's projects devoted Trusted Research Environments (TREs) can directly inform EHDS SPE design. The document equally flags persistent risks. Semantic interoperability of health datasets remains fragmented, and the SPE implementing acts —which will define critical technical requirements— are not due until March 2027. Importantly, since EHDS deliberately refrains from prescribing semantic or technical standards for secondary use data, research communities and EOSC have a concrete voluntary role to fill. The phased timeline for EHDS secondary use provisions (2029–2031) provides a meaningful window to advance this alignment work before full regulatory application.