Thoracoscopic and laparoscopic techniques play a major role in pediatric surgery. However, minimally invasive surgery (MIS) has not yet established itself in pediatric surgical oncology. The authors present a prospective study investigating the role of MIS in children with cancer. All children with abdominal or thoracic tumors requiring surgery were registered between September, 2000 and February, 2002. Decisions regarding procedures and approaches-conventional or minimally invasive-were made by the interdisciplinary team. Data on diagnoses, surgical procedures, complications, and conversion rates were registered prospectively. Seventy-four patients received 78 operations, 21 (26.9%) of the 78 operations were minimally invasive. Seven of 16 tumor biopsies (43.8%) and 9 of 57 tumor resections (15.8%) were performed using MIS, which was also exclusively used for diagnostic interventions. Conversions to standard techniques only occurred in 5 of 9 tumor resections. No major complications were encountered in the MIS group. MIS was practical in every fourth patient in our experience so far. It proved to be an excellent approach in diagnostic interventions and tumor biopsies, whereas efficacy is limited in tumor resections. Further factors (tumor recurrence, trocar site recurrence, tumor growth, and dissemination after CO(2) insufflation) have to be evaluated. Our data encourage the continuation of the study.