Litter usually drops to the ground, but some is retained within the canopy. Mass and CO2 efflux from retained litter may play a significant role in carbon cycling in tropical rainforests where emergent trees with complicated canopy structures are observed. This study aimed to show vertical variation in the mass and CO2 efflux (Rlitter) of the retained litter and examined its contribution to carbon cycling in a Bornean tropical rainforest.