Conceptual　analysis　is　performed　to　examine　the　effects　of　pore　features　on　the　water　continuity　in　unsaturated　porous　systems.　The　roles　of　pore　features　in　relative　chloride　diffusion　coefficient　(Drc)　of　mortar　specimens　at　various　degrees　of　water　saturation　(Sw)　were　studied　based　on　mercury　intrusion　porosimetry　and　resistivity　tests.　It　is　found　that　the　role　of　pore　structure　in　the　Drc-Sw　relationship　is　a　result　of　its　effect　on　the　water　continuity.　Porosity　and　tortuosity　are　not　relevant　to　the　Drc-Sw　relationship.　A　finer　pore　size　distribution　or　lower　pore　connectivity　tends　to　result　in　a　lower　Drc.　The　pore　size　effect　on　the　Drc　is　pronounced　primarily　at　high　Sw,　while　the　Drc　is　dominated　by　the　pore　connectivity　at　low　Sw.　Cement　mortar　with　a　higher　water-to-binder　ratio　shows　larger　chloride　diffusion　at　high　relative　humidity　levels　but　smaller　chloride　diffusion　at　low　relative　humidity　levels.　©　2019