Visual backward masking is a well suited technique to investigate intact and deficient visual information processing. Whereas visual backward masking has been studied extensively in adult populations, there is only a limited number of investigations in adolescents. Subjects were 17 adolescents (age 10-13 years) and 15 adults (18 -32 years) with normal or correct to normal vision. A vernier was presented followed by a masking grating of either 25 or 5 elements. A spatial inhomogeneous 'gap grating' and a temporal inhomogeneous grating were used as well. Performance with the 25 and 5 element grating was strongly deteriorated in adolescents indicating immature visual processing. However, both adolescents and adults were very sensitive to temporal and spatial in homogeneities in the mask indicating intact and complex spatio-temporal processing. Adolescents were retested one year later. The masking deficits of the adolescents had largely disappeared. We suggest that this improvement is associated with an age-related development of specific or non-specific (motivation, attention) factors. The work was supported by Volkswagen Foundation.