This study examines executive function and its relationship to attention dysfunction and working memory. It attempts to document the manifestations of executive function problems in school-related extended processing tasks, such as verbal problem-solving in math and reading of extended passages. Subjects (in grades 1-12) included 49 children with attention deficit disorder (ADD) not receiving medication, 38 ADD children receiving medication, and 50 non-ADD learning-disabled (LD) children. Factor analysis and regression analyses indicated that the underlying processing dynamic was different for each group. In the unmedicated ADD group, extended processing was found to be the primary factor (accounting for even more variance than working memory measures); in the LD group, a psychological proficiency factor was the dominant characteristic; and for the medicated ADD group, the medication appeared to alleviate the dominance of extended processing difficulties. Other findings suggested a phonologically driven correlate of extended processing in the LD subjects in comparison to an attention driven correlate in the ADD groups. Evidence for the possibility of at least two LD sub-types (attention-based LD and language-based LD) was found. Also noted is the impact of late developing frontal lobe neural pathways on the attention-working memory-executive function complex and the development of increasing learning difficulties through adolescence in the ADD population. Includes 54 references. (Author/DB)