The production of Gamma (1S), Gamma (2S) and Gamma (3S) mesons in proton-proton collisions at the centre-of-mass energy of root s = 7 TeV is studied with the LHCb detector. The analysis is based on a data sample of 25 pb(-1) collected at the Large Hadron Collider. The Gamma mesons are reconstructed in the decay mode Gamma -> mu(+)mu(-) and the signal yields are extracted from a fit to the mu(+)mu(-) invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the Gamma transverse momentum p(T) and rapidity y, over the range p(T) < 15 GeV/c and 2.0 < y < 4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be