An investigation is made of the effect of a homogeneous plasma-vacuum narrow transition region on the nature of surface wave propagation along the vacuum channel boundary. Dispersion equations, taking into account the collision damping of surface waves in the region where the wave frequency is equal to LANGMUIR frequency have been obtained. The expressions for damping coefficients of surface waves have been found both for the plane and the cylindrical geometry. Transformation of surface waves into longitudinal oscillations in the transition layer is also obtained. For a period of time, determined by the transition layer width, the surface waves, caused by initial perturbation, have been demonstrated to transform into longitudinal oscillations concentrated in the plasma-vacuum transition layer and directed along the gradient of plasma density.