Abstract: The invention relates to a extendable wind deflector for a sliding roof of a motor vehicle, which comprises a wind deflector profile (15) provided with at least one air guiding wall (16). Said profile is open along the longitudinal extension thereof in at least one area which is oriented away from the air guiding wall (16) and comprises a sealing device (29) along the longitudinal extension thereof which co-operates with the roof section (8) of the vehicle body in at least one operational position. The at least one open area of the wind deflector profile (15) is covered by means of a covering device (25), such that a wind deflector (10) is obtained with a profile which is closed in the cross-section.