Many children experience a catheterization process in pediatric cardiology units due to heart diseases. In this study, we evaluated 8-14 year old children/adolescent treated in Hacettepe University Ihsan Dogramaci Children Hospital Pediatric Cardiology Unit. We explained the steps of catheterization by different photographs before the cardiac catheterization procedure was performed, and it was planned to investigate the effect of this information on the anxiety levels of children and parents. For this purpose, a photographic booklet, showing the steps of procedure, has been prepared. The patients were categorized in two groups as case and control. Detailed information was given to the case group. The children/adolescents and their parents were assessed using state and trait anxiety inventory symptom observation list prepared by the investigators and a questionnaire about the information given to them. The results showed that there was no statistically significant difference between the case and control groups related to anxiety levels. However, there was a significant relationship between age and state anxiety scales in the case group. All of the results were discussed with the support of the literature, and it was concluded that it may be useful to provide detailed training on medical procedures with different educational tools according to the educational levels of children/adolescent and their families and learning skills. Anahtar Kelimeler : cardiac catheterization, anxiety, preoperative preparation