Visual spatial attention was evaluated in 10 dyslexic (8 males and 2 females) and 12 normally reading (9 males and 3 females) children using a response competition procedure (flanker task). When an irrelevant distractor is presented adjacent to a target stimulus, interference is observed when the two stimuli are associated with conflicting responses. In the present study the distractor flanked the target either to the right or to the left. Results showed an asymmetric flanker effect in dyslexics, whereas it was symmetrical in normal readers. Dyslexics exhibited a reduced flanker effect in the left visual field. Such visual field asymmetry is thought to play a crucial role in reading disorders. These results were interpreted as an asymmetric distribution of visual spatial attention, possibly related with a posterior attention mechanism deficit in the right parietal cortex and/or an interhemispheric dysfunction and/or an impairment of cerebellar functions.