The　perception　of　vehicle　ride　comfort　is　influenced　by　the　dynamic　performance　of　full-depth　foam　used　in　many　vehicle　seats.　The　effects　of　the　thickness　of　foam　on　the　dynamic　stiffness　(i.e.,　stiffness　and　damping　as　a　function　of　frequency)　of　foam　cushions　with　three　thicknesses　(60,　80,　and　100mm),　and　the　vibration　transmitted　through　these　cushions　at　the　seat　pan　and　the　backrest　were　measured　with　12　subjects　(6　males　and　6　females).　With　increasing　thickness,　the　stiffness　and　the　damping　of　the　foam　decreased.　With　increasing　thickness　of　foam　at　the　seat　pan,　the　resonance　frequencies　around　4Hz　in　the　vertical　in-line　and　fore-and-aft　cross-axis　transmissibilities　of　the　seat　pan　cushion　and　the　backrest　cushion　decreased.　For　the　conditions　investigated,　it　is　concluded　that　the　thickness　of　foam　at　a　vertical　backrest　has　little　effect　on　the　vertical　in-line　or　fore-and-aft　cross-axis　transmissibilities　of　the　foam　at　either　the　seat　pan　or　the　backrest.　The　frequencies　of　the　primary　resonances　around　4Hz　in　the　vertical　in-line　transmissibility　and　the　fore-and-aft　cross-axis　transmissibility　of　foam　at　the　seat　pan　were　highly　correlated.　Compared　to　sitting　on　a　rigid　seat　pan　with　a　foam　backrest,　sitting　with　foam　at　both　the　seat　pan　and　the　backrest　reduced　the　resonance　frequency　in　the　vertical　in-line　transmissibility　of　the　backrest　foam　and　increased　the　associated　transmissibility　at　resonance,　while　the　fore-and-aft　cross-axis　transmissibility　of　the　backrest　was　little　affected.　Compared　to　sitting　without　a　backrest,　sitting　with　a　rigid　vertical　backrest　increased　the　resonance　frequency　of　the　fore-and-aft　cross-axis　transmissibility　of　the　seat　pan　cushion　and　increased　the　transmissibility　at　resonance.　Relevance　to　industry:　The　transmissibility　of　a　seat　is　determined　by　the　dynamic　properties　of　the　occupant　of　the　seat　and　the　dynamic　properties　of　the　seat.　This　study　shows　how　the　thicknesses　of　foam　at　a　seat　pan　and　foam　at　a　backrest　affect　the　in-line　and　cross-axis　transmissibilities　of　the　foams　at　the　seat　pan　and　the　backrest.　The　findings　have　application　to　the　design　of　vehicle　seats　to　minimise　the　transmission　of　vibration　to　the　body.　©　2015　Elsevier　B.V.