Respiration of CO 2 from soils (R s ) is a major component of the carbon cycle of ecosystems, but understanding is still poor of both the relative contributions of different respiratory sources to R s , and the environmental factors that drive diurnal variations in R s . We measured total and litter-free R s at half-hourly intervals over full 24h periods, and thereafter twice a month for 10 months in a tropical montane cloud forest (TMCF) in Peru. Total R s declined by about 61% during the night as a result of variations in respiration rate in the litter, which were partly correlated with the soil surface air temperature. Most of the diurnal variation of R s in this TMCF appears to be driven by respiration in the litter layer, which contributed 37% to the total soil CO 2 efflux. Total R s rates at this particular site would have been overestimated by 60% if derived from daytime measurements that had not been corrected for diurnal variations in R s .