In this paper, a comprehensive investigation of the stochastic response of a cable-stayed bridge subjected to spatially varying ground motions is performed based on a recently proposed model. The spatial variability of ground motions is considered with incoherence, wave-passage and site-response effects. The importance of the site-response effect, which arises from the difference in the local soil conditions at different support points of the structure, is investigated particularly. Mean of maximum and variance response values obtained from the spatially varying ground motions are compared with those of the specialised cases of the ground motion model. It is pointed out that each component of the spatially varying ground motion model has important effects on the dynamic behaviour of the structure. Therefore, to be more realistic in calculating the bridge responses, the variability of the ground motions should be incorporated in the analysis of long span structures. (C) 2003 Elsevier Science Ltd. All rights reserved.