Abstract This paper reports measurements of relative permeability to methane (CH 4) and carbon dioxide (CO 2) in hydrate-bearing sandstone core samples. The CH 4 (or CO 2) permeability was measured at reservoir conditions for different hydrate and brine saturations. The saturation span ranged from 0.18 to 0.60 (frac.) for CH 4 gas and from 0.37 to 0.70 (frac.) for liquid CO 2. The hydrate saturation ranged from 0.18 to 0.61 (frac.). The growth of hydrates within sandstone pores reduced the permeability for both the CH 4 and CO 2 system significantly, and the relative reduction was more pronounced for lower gas saturations. This effect is currently not included in numerical models of relative permeability in hydrate-bearing sediments and should be considered. The reported measurements are relevant to production-forecasting of methane gas from hydrate reservoirs and CO 2 storage schemes where CO 2 hydrates may provide self-sealing in cold aquifers. Highlights • Measurements of relative permeability to CH 4 and CO 2 in hydrate-bearing Bentheim sandstone cores at reservoir conditions. • The relative permeability to CH 4 (or CO 2) decreased when hydrate formed in the pore space. • No correlation between permeability and hydrate saturation was found for constant CH 4 (or CO 2) saturation. [ABSTRACT FROM AUTHOR]