We have investigated the mobility of bromoform (CHBr3) and chloroform (CHCl3) on amorphous solid water and crystalline ice surfaces, by monitoring their adsorption and desorption behavior using temperature programmed desorption spectroscopy and reflection absorption infrared spectroscopy. Up to its desorption temperature, of 140 K, CHCl3 does not diffuse over the crystalline ice surface, whereas CHBr3 is found to be mobile at temperatures as low as 85 K. The results demonstrate distinct differences between the surface mobility of structurally similar haloform molecules on crystalline ice surfaces, which may have implications to the halocarbon chemistry occurring on atmospheric ice particles. (C) 2004 Elsevier B.V. All rights reserved.