Abstract: An extendible crane boom comprises, in addition to a tubular base boom section (1), a plurality of boom sections (2, 3, 4, 5) telescopically within the base boom section and each composed of a tube and a holder (8, 8', 8", 8"') mounted at an outer end thereof for connecting the tube to a double-acting hydraulic cylinder (9, 9', 9", 9"') with a view to displacing each boom section out of and into an immediately preceding boom section so as to lengthen and shorten, respectively, the crane boom in its entirety. The third and fourth hydraulic cylinders (9", 9"') are located in a first plane which is parallel to the longitudinal extent of the boom and located inwardly of a second plane, in which the first and second hydraulic cylinders (9, 9') are located. This minimizes the overall height of the outermost telescopic boom sections (4, 5), counted as the center distance between the telescopic tube concerned and the associated hydraulic cylinder.