Martensitic-ferritic stainless steels (MPSS) have been proposed to fulfill an existing gap in material selection, caused by the limited corrosion performance of supermartensitic stainless steels and high costs of duplex stainless steels. This kind of steel basically presents a martensitic-ferritic matrix and, depending on heat treatment schedule, small amounts of retained austenite (gamma(ret)), chi-phase (chi), carbides and other deleterious phases can form. Since these microstructure features may affect corrosion behavior in different ways, the influence on hydrogen diffusion in a MESS with different content of retained austenite (gamma(ret)) and chi-phase (chi) was investigated. Samples were submitted to electrochemical hydrogen permeation and thermal desorption spectroscopy (TDS) techniques. As a result, microstructures have shown different behaviors on hydrogen diffusion. The lower hydrogen apparent diffusion coefficient (D-app) was obtained for the sample called retained austenite (RA) with 7% of retained austenite, 20% of ferrite and 73% of martensite. The results of TDS showed that retained austenite plays a role as irreversible hydrogen trapping site. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.