Ballistic deposition simulations of thin film growth were performed. The results of the simulations are compared to experiments of N-2 adsorption by porous amorphous solid water thin films. The simulations are in qualitative agreement with the experimental observations: The porosity of the thin films is controlled by using a collimated beam to vapor deposit the films. Films with normal or near normal growth angles (theta similar to0 degrees) are relatively dense and smooth. Films with larger growth angles are highly porous and the average pore size increases as the growth angle increases. The simulations indicate that for growth angles greater than similar to 70 degrees, adsorption into the largest pores is not possible leading to the experimentally observed maximum in N-2 adsorption by porous amorphous solid water at theta = 70 degrees. (C) 2001 American Institute of Physics.