We report a Molecular Dynamics simulation study of the diffusion process of formaldehyde (CH2O) in proton-disordered ice Ih at atmospheric pressure, in the temperature range 200-273 K. CH2O molecules diffuse in ice predominantly by jumping between B sites (bond-breaking mechanism), but substitutional diffusion can also be observed. At 260 K, the diffusion constant is predicted to be 4 x 10(-7) cm(2)/S with the TIP4P-Ew water model, and 3 x 10(-7) cm(2)/S with the TIP4P/Ice water model. (c) 2006 Elsevier B.V. All rights reserved.