A method of equipping an auxiliary boom arranged on the main boom of a mobile crane with an auxiliary device, wherein - in the vicinity of the head of the main boom a support is mounted on it, by means of which the lifting cable of the main boom may be guided to a pivot point on the auxiliary boom, - the support consists of two luffing supports (8, 9) whose feet are situated close to one another and whose free ends are connected together, - the two luffing supports (8, 9) are permanently connected together by a tension force link strand, - the auxiliary boom is connected to the head of the main boom via an adapter, on which the luffing supports are situated, - the upper and lower luffing supports may be laid flat on the auxiliary boom for transport purposes, - a multi-element connecting rod is permanently connected to the lower luffing support, - the connecting rod is connectable to an adjustment lifting gear via a pulley, characterised by the following method steps: the auxiliary boom is mounted on the head of the main boom, wherein the two luffing supports (8, 9) lie flat on the auxiliary boom, the lifting cable is unwound from the main lifting gear of the mobile crane and connected to the connecting rod, which is permanently connected to the lower luffing support, wherein the two luffing supports are connected together by the tensional force link strand, a winding up of the lifting cable onto the lifting gear occurs, whereby the luffing supports (8 and 9) rise up, the connecting rod is then connected to a flying beam and the lifting cable is unwound so that the beam rises up along a line from the fixed beam to the tip of the lower luffing support, the pulley is thus placed under tension so that the lifting cable can be uncoupled in this position from the connecting rod, the main boom is then raised by means of the luffing cylinder and the adjustment lifting gear is simultaneously unwound so that the distance between the flying beam and the fixed beam increases, the adjusting lifting gear can then be wound up again from a previously fixed main boom angular position so that the distance between the flying beam and fixed beam decreases, whereby the adjustable auxiliary boom rises up from the ground since it is connected to the upper luffing support by means of a further tensional force link strand. - in the vicinity of the head of the main boom a support is mounted on it, by means of which the lifting cable of the main boom may be guided to a pivot point on the auxiliary boom, - the support consists of two luffing supports (8, 9) whose feet are situated close to one another and whose free ends are connected together, - the two luffing supports (8, 9) are permanently connected together by a tension force link strand, - the auxiliary boom is connected to the head of the main boom via an adapter, on which the luffing supports are situated, - the upper and lower luffing supports may be laid flat on the auxiliary boom for transport purposes, - a multi-element connecting rod is permanently connected to the lower luffing support, - the connecting rod is connectable to an adjustment lifting gear via a pulley, the auxiliary boom is mounted on the head of the main boom, wherein the two luffing supports (8, 9) lie flat on the auxiliary boom, the lifting cable is unwound from the main lifting gear of the mobile crane and connected to the connecting rod, which is permanently connected to the lower luffing support, wherein the two luffing supports are connected together by the tensional force link strand, a winding up of the lifting cable onto the lifting gear occurs, whereby the luffing supports (8 and 9) rise up, the connecting rod is then connected to a flying beam and the lifting cable is unwound so that the beam rises up along a line from the fixed beam to the tip of the lower luffing support, the pulley is thus placed under tension so that the lifting cable can be uncoupled in this position from the connecting rod, the main boom is then raised by means of the luffing cylinder and the adjustment lifting gear is simultaneously unwound so that the distance between the flying beam and the fixed beam increases, the adjusting lifting gear can then be wound up again from a previously fixed main boom angular position so that the distance between the flying beam and fixed beam decreases, whereby the adjustable auxiliary boom rises up from the ground since it is connected to the upper luffing support by means of a further tensional force link strand.