Attention processes were studied using a model based on visual searches for a specified element in grids of size 3 x 3 and 7 x 7 cm displayed on a monitor screen. Five age groups took part in the experimental studies: children of five and seven years, a group of 15-year-old adolescents, a group aged 20-35 years, and a group aged over 60 years; a total of 62 subjects took part. Statistical analysis showed that the latter three groups were not different from each other and were used as an adult control group for comparison with results from children. Five types of search were used: one difficult, in which the target was similar to the distractors, and four easy (for adults but not for children), involving seeking a red or a white element in an empty grid and seeking a target markedly different in shape or color from the distractors. The following measures were analyzed: search time, errors (false alarms and misses), and corrected search times allowing for errors. Children performed significantly worse on all measures: they found all types of search difficult, even the search for a single element. The larger number of false alarms (reactions to nonmeaningful signals) was evidence for a deficiency of inhibitory processes in children, these being controlled by the frontal lobes. The larger number of misses in children may be evidence of weakness of selective attention, which is controlled by the parietal and temporal areas of the cortex. These points may indicate that children have an immature attention system, though this would appear to mature completely by age 15 years.