Velocity dispersion curves of leaky surface acoustic waves (LSAW) were calculated using simple models which represented different states of adhesion: perfect bonding, detachment and intrusion of water. The phase velocities of LSAW were found to depend on the boundary conditions between a film and a substrate. Using a scanning acoustic microscope, it was confirmed that the difference of adhesion resulted in differences in the shape of V(z) curves. The phase velocities of LSAW thus obtained were examined in conjunction with theoretical calculations.