Contentious issues in relation to hydrogen uptake and diffusion in metals (primarily steels) are discussed in relation to recent modelling predictions and current understanding. Topics highlighted include optimising charging conditions in hydrogen permeation measurements, limits to hydrogen uptake with increase in charging current density, irreversible traps and beneficial traps, the effective diffusion coefficient, the primary source of hydrogen in relation to hydrogen assisted cracking, and outstanding challenges in modelling hydrogen diffusion. Crown Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.