The effects of mild/moderate iodine deficiency during the fetal/neonatal life on neuropsychological performances are still poorly defined. In this research we analyzed some parameters of cognitive performance with sensitive psychometric tests in children living in an area with moderate iodine deficiency. Each subject was submitted to the following neuropsychological tests: 1) a reaction time (RT) session, 2) the block design subtest of the WISC-R, 3) the coding subtest of the WISC-R. No significant difference was found between children with mild iodine deficiency and controls, for block design and coding tests. On the other hand controls had significantly faster RTs. Our data show that exposure to mild iodine deficiency in fetal/neonatal life does not affect general cognitive performance but influences the velocity of motor response to visual stimuli, which may be due to an alteration of the efficiency of the information processing mechanism.