A method is provided for treating turbine blades having holes for discharging cooling air. A protective layer is provided and then the holes that are partly or completely closed by the protective layer are opened again. Coordinates concerning the position of the holes are acquired before the protective layer is applied using a laser triangulation sensor using a light source generating a light beam and a light detector. The data obtained is used after application of the protective layer to control a removal device for removing protective layer partly or wholly covering the holes. Each hole is measured by the light beam being shone into the hole in different positions in relation to the longitudinal mid-axis of the latter. The light beam is shone into the respective hole in a plane at at least three different angles to the longitudinal mid-axis thereof.