A movement support system for an openable roof of a vehicle, in particular a boat, for mounting at the site of an opening formed in the roof of the vehicle for movably supporting at least one closure element for selectively covering the opening. The system includes a pair of elongate support modules configured as rectilinear bars, for mounting on the roof of the vehicle on opposite sides of the opening. Each support element has a track element extending substantially parallel to the support element with one or more carriage elements, connectable to the closure element, mounted thereon for longitudinal sliding. The system also includes a transmission for imparting movement controlled by a motor to at least one of the carriage elements. The transmission includes a belt member connected to at least one of the carriage elements and closed in a loop about two end pulleys so as to form two belt branches extending longitudinally along the support members, which are spaced by a distance substantially the same as a transverse dimension of the carriage elements.