Within the MIDAIR project 15 European dairy model farms were defined and a simulation model was developed that calculates carbon and nitrogen flows on dairy farms.The model farms represent pairs of organic and conventional dairy farms in five European (EU15) dairy production regions: The Atlantic, the Continental, the Boreal, the Pre-Alpine and the Mediterranean region. The model farms are designed for use in farm-scale modelling of greenhouse gas emissions from dairy farms. Currently the model farms have been used as input for the FarmGHG model. However, the farms may be readily used for similar modelling work, applying different models.FarmGHG is a model of carbon (C) and nitrogen (N) flows on dairy farms. The model was designed to allow quantification of all direct and indirect gaseous emissions from dairy farms, so that it can be used for assessment of mitigation measures and strategies. The imports, exports and flow of all products through the internal chains on the farm are modelled. The model thus allows assessments of emission from the production unit and all pre-chains. The model includes N balance, and allows calculation of environmental effect balances for GHG emissions (CO2, CH4 and N2O) and eutrophication (nitrate and NH3). The FarmGHG model can be used for further investigations in dairy production.