The invention relates to a method of raising a telescopic boom of a mobile crane having a luffing fly jib and having a spatial boom guying. To be able to raise particularly long luffing fly jib systems together with the telescopic boom here, in accordance with the invention the telescopic boom is first telescoped outwardly to its desired length. In this position, all the telescopic sections are bolted to one another and the spatial guying is tensioned before the raising of the luffing fly jib pivotally connected to the telescopic boom.