We investigate the influence of the phase front curvature of an input light beam on the transverse localization of light, choosing an evanescently coupled disordered one-dimensional semi-infinite waveguide lattice as an example. Our numerical study reveals that a finite phase front curvature of the input beam does indeed play an important role and it could degrade the quality of light localization in a disordered dielectric structure. More specifically, a faster transition from the ballistic mode of beam propagation due to diffraction to a characteristic localized state is observed in the case of a continuous wave (CW) beam whose phase front is plane, as compared to one having a curved phase front. © 2012 IOP Publishing Ltd.