Respiration of CO2 from soils (Rs) 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 Rs, and the environmental factors that drive diurnal variations in Rs. We measured total and litter-free Rs at half-hourly intervals over full 24 h periods, and thereafter twice a month for 10 months in a tropical montane cloud forest (TMCF) in Peru. Total Rs 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 Rs in this TMCF appears to be driven by respiration in the litter layer, which contributed 37% to the total soil CO2 efflux. Total Rs 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 Rs. Crown Copyright © 2009.