We rigorously derive a mean-field model for Ostwald ripening in two-dimensional systems that arise in the growth of thin metallic films. This extends the classical LSW theory in two ways. First, it shows that an LSW-type model is also valid in two dimensions, even though the formal derivation seems less convincing than in three dimensions. Second, it clarifies the regime of validity and provides an inhomogeneous extension. (C) 2001 John Wiley & Sons, Inc.