A door can be an obstacle when it does not meet the needs of its users. The purpose of the work was to determine the dimensional and functional requirements of the use of internal doors in public buildings by people with mobility impairments and with service dogs. This paper addresses three subjects: (i) human and canine functioning, (ii) accessibility standards, and (iii) comparison between personal and environmental components. As a result proposals for the improvement of the Portuguese accessibility standard are presented.