A Letter Cancellation task from the Neuropsychological Diagnostic Battery of the University of Habana (DNUH-2000-R) was studied on 792 children and shown to be an appropriate diagnostic tool in classifying subjects according to sex, age, and grade level in the represented population. A method of response analysis is introduced with the purpose of differentiating attentional characteristics of the subjects. An alternative update of the percentile ranks on this test is also presented.