The invention provides a crane boom segment for assembly of a crane boom, a method for assembling a crane boom. Crane boom segment (20) for assembly of a crane boom by interconnection of multiple crane boom segments from a transport configuration to an operational configuration. The crane boom segment (20) comprises a first and second planar latticed truss (21, 22), each with two chords (21 a, 21 b, 22a, 22b) between which permanent lacing elements (21c, 22) extend, wherein both chords of each planar latticed truss (21, 22) comprise segment connection parts (26) at their head ends allowing crane boom segments to be connected to each other in series, and wherein in the operational configuration the first and second planar latticed trusses are provided at opposite sides of the longitudinal axis of the crane boom segment (40). A crane boom segment (40) further comprises a first and second lattice web (23, 24), each lattice web (23, 24) connectable to one of the chords of the first planar latticed truss (21, 22) and one of the chords of the second planar latticed truss. The invention also relates to a modular crane (90), comprising a travelling base frame (95) which allows for travel of said crane over a surface, and a crane boom assembled from crane boom segments, one end of the crane boom being hingedly connected about a substantially horizontal pivot axis, to said travelling base frame.