BACKGROUND: Managing aorto-ostial coronary lesions during percutaneous coronary interventions (PCI) presents significant challenges due to complex anatomy, catheter instability, and risks of stent misplacement. AIMS: The OSTIAL pivotal study aimed to assess the feasibility and precision of the floating balloon technique for optimizing stent placement in aorto-ostial lesions (AOL), with post-procedural coronary computed tomography angiography (CCTA) used to evaluate stent positioning. METHODS: This prospective, dual-center observational study included 12 patients undergoing PCI for AOL using the floating balloon technique. The technique stabilizes the guiding catheter by positioning a balloon in the aorta, thereby defining the aorto-ostial landing zone (AOLZ) for precise stent placement. Post-procedural CCTA were systematically performed to assess the positioning of the stent. The primary outcome was technical success including optimal stent placement within the AOLZ and proximal anatomy-dependent geographic miss. RESULTS: The primary outcome was achieved in 83% of cases, with 66% showing complete AOLZ coverage and 17% classified as a proximal anatomy-dependent geographic miss. Proximal procedure-dependent geographic miss occurred in only 17% of cases, with limited stent protrusion into the aorta (2.3 and 2.9 mm). CONCLUSIONS: The floating balloon technique demonstrated feasibility and precision in optimizing stent placement in AOL, as assessed by CCTA. It offers a promising, cost-effective, and practical alternative to other techniques. Larger studies are required to confirm its efficacy and long-term benefits.