A lithographic apparatus component, such as a metrology system or an optical element (e.g., a mirror) is provided with a temperature control system for controlling deformation of the component. The control system includes channels provided close to a surface of the component through which a two phase cooling medium is supplied. The metrology system measures a position of at least a moveable item with respect to a reference position and includes a metrology frame connected to the reference position. An encoder is connected to the moveable item and constructed and arranged to measure a relative position of the encoder with respect to a reference grid. The reference grid may be provided directly on a surface of the metrology frame. A lithographic projection apparatus may have the metrology system for measuring a position of the substrate table with respect to the projection system.