Gaps within woodland canopies have important ecological roles and their spatial characteristics influence regeneration processes and the diversity and distribution species. This paper investigates the potential of airborne imaging spectrometer data for characterizing the spatial properties of gaps within deciduous woodlands. Imagery obtained in summer with an Compact Airborne Spectrographic Imager (CASI) was classified to produce an accurate map of canopy gaps within several deciduous woodlands. Imagery obtained in winter proved much less informative. Principal components analysis (PCA) of separate and combined summer and winter images revealed PCs that provided information on woodland canopy structure and could be classified to give an improved delineation of canopy gaps. The spatial characteristics within the woodlands were quantified using a raster-based GIS and pattern-process relationships were used to infer the relative ecological status of the different woodlands. The ability of the aircraft to fly at short notice and the high sensitivity and high spatial and spectral resolution of the airborne spectrometer offered many advantages over broad-band satellite sensors for this application.