A single molecule in an inhomogeneous environment is studied theoretically using phenomenological theory. The molecule is located on a planar glass substrate and a finite sized, three dimensional object is scanned over the molecule at different heights. Lifetime and quantum yield are calculated as a function of the lateral position of the object. The analysis is based on a new field expansion method using Green’s functions of a layered reference system as basis functions. It is found that, near the edges of the object, the molecular lifetime is highly sensitive to the orientation of the transition dipole. ©1996 American Institute of Physics.