The use of Hydrogen as a fuel is widely discussed today with stainless steels able to be used for tubing and as fittings in various systems. The application areas vary from tubing and fittings in vehicles, filling stations, production or storages facilities. In all applications resistance against hydrogen embrittlement is a key prerequisite. Earlier the susceptibility to hydrogen embrittlement of three austenitic stainless steels tested by different SSRT methods has been reported: electrochemical charged, thermal pre-charged and in situ testing in 85 to 87.5 MPa hydrogen gas at -40°C. The low nickel versions of UNS S31603 experienced brittle fracture whereas the high nickel version of UNS S31603 as well as UNS S31675 had ductile fractures. The appearance of the fracture surface in SEM indicates that all test methods promote ingress of hydrogen to the center of the specimen. In this work, study of the deformation mechanisms has been performed by EBSD obtained 5 mm from the fracture. The study reveals that the low nickel version of UNS S31603 experiences formation of deformation induced martensite, the high nickel version of UNS S31603 shows no martensite but produces twinning. UNS S31675 which has a small grain size shows no formation of martensite and only small degree of twinning. The deformation structures are discussed with respect to the outcome of the SSRT-testing and austenite stability.