New technologies such as Light Detection And Ranging (LiDAR) provide high resolution digital elevation data. These data offer new possibilities in the field of terrain modelling and analysis. However, not very much is known about the effects when these data are used to compute broadly applied terrain derivatives. In this paper the sensitivity of the Topographic Wetness Index (TWI) and its two constituting components gradient and Specific Catchment Area (SCA) regarding the resolution of LiDAR-based elevation data is examined. For coarser resolutions a shift in the TWI distribution to higher values is noted. TWI distributions at different resolutions differ significantly from each other. These findings have an impact on aspatial and spatial modelling based on the TWI.