The relaxed eddy-accumulation (REA) technique was specially adapted to a high-performance liquid chromatographer (enzymatic method) and scrubbing coils to measure concentrations and fluxes of hydrogen peroxide (H 2 O 2 ) and organic peroxides with a carbon chain ⩽C 4 , of which only methylhydroperoxide (MHP) and hydroxymethylhydroperoxide (HMHP) were detected. Flux measurements were carried out above the canopy of a Norway spruce forest in Germany (775m a.s.l.) in NE Bavaria, Germany, during the BEWA2000 research cluster in summer 2001. This period was characterised by H 2 O 2 maximum mixing ratios of 1ppb and mixing ratios of organic peroxides below 200ppt. Daily mean H 2 O 2 deposition fluxes of −0.8±0.3nmolm −2 s −1 , MHP of −0.03±0.03nmolm −2 s −1 and HMHP of −0.7±0.5nmolm −2 s −1 were obtained. Profile measurements were performed as a qualitative comparison of the controlling mechanism of the surface exchanges. The REA as well as the profile measurements show that during daylight the surface exchanges of H 2 O 2 and MHP over coniferous forest are mainly controlled by dry deposition. The high H 2 O 2 dry-deposition velocity suggests a negligible surface uptake resistance for H 2 O 2 , whereas the significantly smaller MHP-deposition velocity indicates a significant surface uptake resistance. However, nighttime surface exchanges of these compounds should be further investigated since the in-canopy ozonolysis reaction is expected to affect exchanges. HMHP REA flux measurements show mainly deposition, whereas the ones based on the profile method suggest in-canopy chemical production.