Ambient gas-phase and snow-phase measurements of formaldehyde (HCHO) wereconducted at Summit, Greenland, during several summers, in order to understand the roleof air-snow exchange on remote tropospheric HCHO and factors that determine snowpackHCHO. To investigate the impact of the known snowpack emission of HCHO, a gas-phasemodel was developed that includes known chemistry relevant to Summit and that isconstrained by data from the 1999 and 2000 field campaigns. This gas-phase-only modeldoes not account for the high ambient levels of HCHO observed at Summit for severalprevious measurement campaigns, predicting approximately 150 ppt from predominantlyCH4 chemistry, which is ~2550% of the observed concentrations for several years.Simulations were conducted that included a snowpack flux of HCHO based on HCHOflux measurements from 2000 and 1996. Using the fluxes obtained for 2000, thesnowpack does not appear to be a substantial source of gas-phase HCHO in summer. The1996 flux estimates predict much higher HCHO concentrations, but with a strong dielcycle that does not match the observations. Thus, we conclude that, although the flux ofHCHO from the surface likely has a significant impact on atmospheric HCHO above thesnowpack, the timedependent fluxes need to be better understood and quantified. It isalso necessary to identify the HCHO precursors so we can better understand the nature andimportance of snowpack photochemistry.