Cavity size distributions at different locations in three proteins have recently been determined from molecular dynamics [B. Pereira, S. Jain, S. Garde, J. Chem. Phys. 124 (2006) 074704]. They show a single peak, corresponding to the most probable cavity size and occurring at different radii as a consequence of the heterogeneity of protein interior. These distributions, when translated to the origin, prove to possess a very similar width that should be a common property of protein interior. In this Letter, it is shown that these 'experimental' translated cavity size distributions can be reproduced by a suitable application of scaled particle theory. (c) 2006 Elsevier B.V. All rights reserved.