The stand-up unit (10) comprises a support (21), a stand-up frame (13), which is articulated on the support (21) and has a seat carrier (23) carrying a seat (17), and a backrest carrier (25) carrying a backrest (19). Furthermore, a first lever parallelogram (27) is provided in order to maintain the backrest (19) upright in any position. The backrest (19) can be displaced by the first lever parallelogram (27) by means of a rod (30), in order to ensure that no undesirable relative movement occurs between the backrest (19) and the back of the user when getting up or sitting down. A second lever parallelogram (29) controls the movement of the seat (17) when getting up and sitting down to ensure that no relative movement develops between the seat (17) and buttocks of the user. The stand-up unit may be provided with a base to serve as a chair, particularly a therapy chair. The stand-up unit, however, may also serve as a stand-up wheelchair, when connected to an undercarriage. Spring joint elements (59, 61) support the standing up.