Tower-based measurements of hydrogen peroxide (H2O2) and formaldehyde (HCHO)exchange were performed above the snowpack of the Greenland ice sheet. H2O2 andHCHO fluxes were measured continuously between June 16 and July 7, 2000, at theSummit Environmental Observatory. The fluxes were determined using coilscrubber-aqueous phase fluorometry systems together with micrometeorologicaltechniques. Both compounds exhibit strong diel cycles in the observed concentrationsas well as in the fluxes with emission from the snow during the day and the eveningand deposition during the night. The averaged diel variations of the observed fluxeswere in the range of +1.3 · 10^13 molecules m^-2 s^-1 (deposition) and-1.6 · 10^13 molecules m^-2 s^-1 (emission) for H2O2 and +1.1 · 10^12molecules m^-2 s^-1 and -4.2 · 10^12 molecules m^-2 s^-1 for HCHO, while the netexchange per day for both compounds were much smaller. During the study period of22 days on average 0.8 (+4.6/-4.3) · 10^17 molecules m^-2 of H2O2 were depositedand 7.0 (+12.6/-12.2) · 10^16 molecules m^-2 of HCHO were emitted from the snowper day. A comparison with the inventory in the gas phase demonstrates that theexchange influences the diel variations in the boundary layer above snow covered areas.Flux measurements during and after the precipitation of new snow shows that less than16 % of the H2O2 and more than 25 % of the HCHO originally present in the new snowwere available for fast release to the ABL within hours after precipitation. This releasecan effectively disturb the normally observed diel variations of the exchange betweenthe surface snow and the atmosphere, thus perturbing also the diel variations ofcorresponding gas phase concentrations.