 After obtaining written informed consent parent and assent child, screening procedures will include administration of an abbreviated intellectual test battery, a working memory battery, and a computerized attention measure to the survivor see specific Measures below. Our goal is to enroll 24 12 ALL, 12 brain tumor participants in the intervention phase of this prospective pilot study. To reach this goal, we anticipate needing to screen approximately 50 survivors, though enrollment will end when, or continue until, 24 eligible participants are identified and randomized to the intervention phase. Parents will complete questionnaire measures regarding their childs adaptive, behavioral, emotional, and attentional functioning. Follow-up interviewing will be conducted to clarify any potential problems identified on the questionnaires. The entire screening procedure is estimated to take approximately 90 minutes for the survivor and 30-45 minutes for parents. To maximize efficiency, two study personnel will work with families - one will complete testing with the child, while the other will complete questionnaires and follow-up interviewing with the parent. The design will be a double-blind, placebo-controlled trial in which half of the participants will be randomized to the intervention condition and half will receive a comparison computer program. Specifically, participants assigned to the comparison placebo condition will complete a modified version of the CT at home. The treatment and comparison CT programs begin identically, at the lowest difficulty level. Those in the treatment condition will complete activities of increasing difficulty over the intervention period. Those in the placebo condition, in contrast, will complete the same basic tasks during each session of the intervention, regardless of performance. In this way, a true estimate can be obtained of the efficacy of the treatment program. 