Deformation bands represent a common type of strain localization in deformed porous sandstones and occur as single structures, as clusters, and in fault damage zones. They show from zero to six orders of magnitude reduction in permeability and may therefore potentially affect fluid flow. We here present mathematical calculations indicating that uncommonly high permeability contrasts and/or exceptionally high band concentrations are required for deformation bands to significantly affect production rate. We also present field observations showing rapid variations in porosity and permeability along deformation bands and deformation-band zones alike. Furthermore, many paleofluid fronts seen in the field are unaffected or only gently affected by deformation bands. Together, these calculations and observations suggest that their function during reservoir production is small or negligible in most cases. Structural complications caused by subseismic faulting and complex fault anatomy are more likely to cause production problems, in addition to stratigraphic and diagenetic effects. Nevertheless, the arrangement and orientation of deformation bands may have an effect on the flow pattern and reservoir sweep. In cases where deformation bands do cause production problems, it may be possible to resolve these by means of hydraulic fracturing.