The diffuse reflectance infrared Fourier transform spectra of solid complexes 1-indanone/beta -cyclodextrin (beta -CD), 2-indanone/beta -CD, 1'-acetonaphthone/beta -CD, and 2'-acetonaphthone/beta -CD exhibit a series of very important effects induced by complexation. For the complexes 1-indanone/beta -CD, 2-indanone/beta -CD, and 2'-acetonaphthone/beta -CD, a dramatic decrease on the intensity of the band assigned to the water deformation mode was observed, showing that these probes are deeply included in the cyclodextrin cavity, displacing the crystallization water. Hydrogen bonding interactions involving the ketone carbonyl and the hydroxyl groups of beta -CD are responsible for the stabilization of the complexes 1-indanone/beta -CD and 2'-acetonaphthone/beta -CD In what concerns the complexes 2-indanone/beta -CD and 1'-acetonaphthone/beta -CD, it is suggested that they are stabilized only by London interactions between the aromatic ring and the cyclodextrin cavity.