Inspection time (IT) measures speed of information processing without the confounding influence of motor speed. While IT has been found to relate to cognitive abilities in adults and older children, no measure of IT has been validated for use with children younger than 6 years. This study examined the validity of a new measure of IT for preschool children. N = 71 4-year-old children completed the new IT task and standardized measures of fluid ability, visuospatial ability, and speed of processing. N = 50 adults completed the same tasks and, additionally, a standard IT task. Results showed that the new IT task is a stable, reliable measure of IT in 4-year-old children. The new task had reasonable concurrent validity with the standard IT task in adults and the relationships between cognitive abilities, particularly general cognitive ability, and IT are sufficiently similar in young children and adults to suggest that the new IT task may be a useful tool for research in populations where IT was previously not measurable.