The performance of a snow pack structure model SNOWPACK was studied in five locations around Finland during two winters. Reasonable agreement between modelled and observed snow depth and snow pack structure evolution was found in all other locations except in coastal Santala. Agreement grew when going towards the north; better agreements were obtained during the early winter than during the melting period. Several test runs with changed input data were done for Hyytiälä. Water equivalent, temperature, grain form and grain size were the most sensitive of the model output quantities to changes in the input data. The use of measured precipitation instead of snow depth for driving the mass balance or the use of different radiation schemes had relatively large effects on the model output. Model sensitivity was high when many phase changes were involved such as during the melting phase in spring or in temperate climate zones.